diff --git a/include/doublen.h b/include/doublen.h
index 9c3bf96773..cc5b5d7379 100644
--- a/include/doublen.h
+++ b/include/doublen.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * doublen.h
- * Internal types used for the average and centroid temporal aggregates.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file doublen.h
+ * Internal types used in particular for computing the average and centroid
+ * temporal aggregates.
+ */
+
 #ifndef __DOUBLEN_H__
 #define __DOUBLEN_H__
 
diff --git a/include/lifting.h b/include/lifting.h
index 8b3f496122..05020059c6 100644
--- a/include/lifting.h
+++ b/include/lifting.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * lifting.c
- * Generic functions for lifting functions and operators on temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file lifting.c
+ * Generic functions for lifting functions and operators on temporal types.
+ */
+
 #ifndef __LIFTING_H__
 #define __LIFTING_H__
 
diff --git a/include/oidcache.h b/include/oidcache.h
index 15edd06916..c3cc4e6644 100644
--- a/include/oidcache.h
+++ b/include/oidcache.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * oidcache.h
- * Functions for building a cache of type and operator Oids.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file oidcache.h
+ * Functions for building a cache of type and operator Oids.
+ */
+
 #ifndef OIDCACHE_H
 #define OIDCACHE_H
 
diff --git a/include/period.h b/include/period.h
index 072d217590..8cf9d4e0ec 100644
--- a/include/period.h
+++ b/include/period.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * period.h
- * Basic routines for timestamptz periods
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,6 +26,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file period.h
+ * Basic routines for time periods composed of two `TimestampTz` values and
+ * two Boolean values stating whether the bounds are inclusive or not.
+ */
+
 #ifndef __PERIOD_H__
 #define __PERIOD_H__
 
@@ -79,7 +82,7 @@ extern void period_shift_tscale(Period *result, const Interval *start,
 
 /* period -> interval */
 
-extern Datum period_timespan(PG_FUNCTION_ARGS);
+extern Datum period_duration(PG_FUNCTION_ARGS);
 
 /* Functions for defining B-tree index */
 
@@ -109,7 +112,7 @@ extern void period_set(Period *p, TimestampTz lower, TimestampTz upper,
   bool lower_inc, bool upper_inc);
 extern Period *period_copy(const Period *p);
 extern float8 period_to_secs(TimestampTz t1, TimestampTz t2);
-extern Interval *period_timespan_internal(const Period *p);
+extern Interval *period_duration_internal(const Period *p);
 extern Period **periodarr_normalize(Period **periods, int count, int *newcount);
 extern Period *period_super_union(const Period *p1, const Period *p2);
 extern void period_expand(Period *p1, const Period *p2);
diff --git a/include/periodset.h b/include/periodset.h
index 2933ae2370..4da01ea86a 100644
--- a/include/periodset.h
+++ b/include/periodset.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * periodset.c
- * Basic functions for set of periods.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file periodset.c
+ * Basic functions for set of disjoint periods.
+ */
+
 #ifndef __PERIODSET_H__
 #define __PERIODSET_H__
 
@@ -76,6 +78,7 @@ extern PeriodSet *timestampset_to_periodset_internal(const TimestampSet *ts);
 
 extern Datum periodset_mem_size(PG_FUNCTION_ARGS);
 extern Datum periodset_timespan(PG_FUNCTION_ARGS);
+extern Datum periodset_duration(PG_FUNCTION_ARGS);
 extern Datum periodset_num_periods(PG_FUNCTION_ARGS);
 extern Datum periodset_start_period(PG_FUNCTION_ARGS);
 extern Datum periodset_end_period(PG_FUNCTION_ARGS);
diff --git a/include/rangetypes_ext.h b/include/rangetypes_ext.h
index 15666179d9..ca4f5efbef 100644
--- a/include/rangetypes_ext.h
+++ b/include/rangetypes_ext.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * rangetypes_ext.h
- * Extension of operators for range types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file rangetypes_ext.h
+ * Extended operators for range types.
+ */
+
 #ifndef __RANGETYPES_EXT_H__
 #define __RANGETYPES_EXT_H__
 
diff --git a/include/tbool_boolops.h b/include/tbool_boolops.h
index 276acfc085..a017386cfa 100644
--- a/include/tbool_boolops.h
+++ b/include/tbool_boolops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tbool_boolops.h
- * Temporal Boolean operators (and, or, not).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tbool_boolops.h
+ * Temporal Boolean operators (and, or, not).
+ */
+
 #ifndef __TBOOL_BOOLOPS_H__
 #define __TBOOL_BOOLOPS_H__
 
diff --git a/include/tbox.h b/include/tbox.h
index 3ec264bfb3..938611fe7d 100644
--- a/include/tbox.h
+++ b/include/tbox.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tbox.h
- * Functions for temporal bounding boxes.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,6 +26,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tbox.h
+ * Functions for temporal bounding boxes.
+ */
+
 #ifndef __TBOX_H__
 #define __TBOX_H__
 
diff --git a/include/temporal.h b/include/temporal.h
index b2dff5f7ff..6b1e42e689 100644
--- a/include/temporal.h
+++ b/include/temporal.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal.h
- * Basic functions for temporal types of any subtype.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal.h
+ * Basic functions for temporal types of any subtype.
+ */
+
 #ifndef __TEMPORAL_H__
 #define __TEMPORAL_H__
 
@@ -88,6 +90,9 @@
 #define BBOX_TEST_NO    false
 
 /** Symbolic constants for the make functions */
+#define MERGE           true
+#define MERGE_NO        false
+
 #define NORMALIZE       true
 #define NORMALIZE_NO    false
 
@@ -486,7 +491,7 @@ extern void ensure_increasing_timestamps(const TInstant *inst1,
   const TInstant *inst2, bool strict);
 extern void ensure_same_overlapping_value(const TInstant *inst1,
   const TInstant *inst2);
-extern void ensure_valid_tinstantarr(TInstant **instants, int count);
+extern void ensure_valid_tinstantarr(TInstant **instants, int count, bool merge);
 extern void ensure_valid_tsequencearr(TSequence **sequences, int count);
 
 /* Input/output functions */
diff --git a/include/temporal_aggfuncs.h b/include/temporal_aggfuncs.h
index 0a5288094e..441a8dcd3c 100644
--- a/include/temporal_aggfuncs.h
+++ b/include/temporal_aggfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_aggfuncs.h
- * Temporal aggregate functions
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_aggfuncs.h
+ * Temporal aggregate functions
+ */
+
 #ifndef __TEMPORAL_AGGFUNCS_H__
 #define __TEMPORAL_AGGFUNCS_H__
 
diff --git a/include/temporal_analyze.h b/include/temporal_analyze.h
index 02d401d957..cebe2d3eb0 100644
--- a/include/temporal_analyze.h
+++ b/include/temporal_analyze.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_analyze.h
- * Functions for gathering statistics from temporal alphanumeric columns
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -25,8 +22,13 @@
  * AN "AS IS" BASIS, AND UNIVERSITE LIBRE DE BRUXELLES HAS NO OBLIGATIONS TO 
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. 
  *
- *-------------------------------------------------------------------------
+ *****************************************************************************/
+
+/**
+ * @file temporal_analyze.h
+ * Functions for gathering statistics from temporal alphanumeric columns
  */
+
 #ifndef __TEMPORAL_ANALYZE_H__
 #define __TEMPORAL_ANALYZE_H__
 
diff --git a/include/temporal_boxops.h b/include/temporal_boxops.h
index 02be75855d..cfed3f0c0a 100644
--- a/include/temporal_boxops.h
+++ b/include/temporal_boxops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_boxops.h
- * Bounding box operators for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_boxops.h
+ * Bounding box operators for temporal types.
+ */
+
 #ifndef __TEMPORAL_BOXOPS_H__
 #define __TEMPORAL_BOXOPS_H__
 
diff --git a/include/temporal_compops.h b/include/temporal_compops.h
index e2457ebc03..17d6cad0a1 100644
--- a/include/temporal_compops.h
+++ b/include/temporal_compops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_compops.h
- * Temporal comparison operators (=, <>, <, >, <=, >=).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_compops.h
+ * Temporal comparison operators (=, <>, <, >, <=, >=).
+ */
+
 #ifndef __TEMPORAL_COMPOPS_H__
 #define __TEMPORAL_COMPOPS_H__
 
diff --git a/include/temporal_gist.h b/include/temporal_gist.h
index 385b32b63f..01a13b2f82 100644
--- a/include/temporal_gist.h
+++ b/include/temporal_gist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_gist.c
- * Quad-tree SP-GiST index for temporal boolean and temporal text types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_gist.h
+ * Quad-tree SP-GiST index for temporal boolean and temporal text types.
+ */
+
 #ifndef __TEMPORAL_GIST_H__
 #define __TEMPORAL_GIST_H__
 
diff --git a/include/temporal_parser.h b/include/temporal_parser.h
index 2420a7041d..61b9cb9a4e 100644
--- a/include/temporal_parser.h
+++ b/include/temporal_parser.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_parser.h
- * Functions for parsing temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_parser.h
+ * Functions for parsing temporal types.
+ */
+
 #ifndef __TEMPORAL_PARSER_H__
 #define __TEMPORAL_PARSER_H__
 
diff --git a/include/temporal_posops.h b/include/temporal_posops.h
index d4d4d48df8..0533934f12 100644
--- a/include/temporal_posops.h
+++ b/include/temporal_posops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_posops.h
- * Relative position operators for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_posops.h
+ * Relative position operators for temporal types.
+ */
+
 #ifndef __TEMPORAL_POSOPS_H__
 #define __TEMPORAL_POSOPS_H__
 
diff --git a/include/temporal_selfuncs.h b/include/temporal_selfuncs.h
index cc64eaad37..9d30779076 100644
--- a/include/temporal_selfuncs.h
+++ b/include/temporal_selfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_selfuncs.h
- * Selectivity functions for the temporal types
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_selfuncs.h
+ * Selectivity functions for temporal types
+ */
+
 #ifndef __TEMPORAL_SELFUNCS_H__
 #define __TEMPORAL_SELFUNCS_H__
 
diff --git a/include/temporal_spgist.h b/include/temporal_spgist.h
index e8fe154464..e2516741fb 100644
--- a/include/temporal_spgist.h
+++ b/include/temporal_spgist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_spgist.c
- * Quad-tree SP-GiST index for temporal boolean and temporal text types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_spgist.c
+ * Quad-tree SP-GiST index for temporal boolean and temporal text types.
+ */
+
 #ifndef __TEMPORAL_SPGIST_H__
 #define __TEMPORAL_SPGIST_H__
 
diff --git a/include/temporal_util.h b/include/temporal_util.h
index 22feb7dbc7..7c30c8fd78 100644
--- a/include/temporal_util.h
+++ b/include/temporal_util.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_util.c
- * Miscellaneous utility functions for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_util.c
+ * Miscellaneous utility functions for temporal types.
+ */
+
 #ifndef __TEMPORAL_UTIL_H__
 #define __TEMPORAL_UTIL_H__
 
diff --git a/include/temporal_waggfuncs.h b/include/temporal_waggfuncs.h
index 56145f9b5b..078b197fbe 100644
--- a/include/temporal_waggfuncs.h
+++ b/include/temporal_waggfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_waggfuncs.c
- * Window temporal aggregate functions
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_waggfuncs.c
+ * Window temporal aggregate functions
+ */
+
 #ifndef __TEMPORAL_WAGGFUNCS_H__
 #define __TEMPORAL_WAGGFUNCS_H__
 
diff --git a/include/temporaltypes.h b/include/temporaltypes.h
index 0f3567ff2f..eff192be12 100644
--- a/include/temporaltypes.h
+++ b/include/temporaltypes.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporaltypes.h
- * Functions for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporaltypes.h
+ * General functions for temporal types.
+ */
+
 #ifndef __TEMPORALTYPES_H__
 #define __TEMPORALTYPES_H__
 
diff --git a/include/time_analyze.h b/include/time_analyze.h
index 075e7198c4..2fc1c42b17 100644
--- a/include/time_analyze.h
+++ b/include/time_analyze.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_analyze.h
- * Functions for gathering statistics from time type columns
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file time_analyze.h
+ * Functions for gathering statistics from time type columns
+ */
+
 #ifndef __TIME_ANALYZE_H__
 #define __TIME_ANALYZE_H__
 
diff --git a/include/time_gist.h b/include/time_gist.h
index b00aa15ac0..ee8d8eff0c 100644
--- a/include/time_gist.h
+++ b/include/time_gist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_gist.c
- * R-tree GiST index for time types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file time_gist.c
+ * R-tree GiST index for time types.
+ */
+
 #ifndef __TIME_GIST_H__
 #define __TIME_GIST_H__
 
diff --git a/include/time_selfuncs.h b/include/time_selfuncs.h
index 22f86075ff..80eaa140eb 100644
--- a/include/time_selfuncs.h
+++ b/include/time_selfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_selfuncs.c
- * Functions for selectivity estimation of time types operators
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file time_selfuncs.c
+ * Functions for selectivity estimation of time types operators
+ */
+
 #ifndef __TIME_SELFUNCS_H__
 #define __TIME_SELFUNCS_H__
 
diff --git a/include/time_spgist.h b/include/time_spgist.h
index 70cb076773..968b4f8efb 100644
--- a/include/time_spgist.h
+++ b/include/time_spgist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_spgist.h
- * Quad-tree SP-GiST index for time types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file time_spgist.h
+ * Quad-tree SP-GiST index for time types.
+ */
+
 #ifndef __TIME_SPGIST_H__
 #define __TIME_SPGIST_H__
 
diff --git a/include/timeops.h b/include/timeops.h
index 7696ead261..9ac46386fc 100644
--- a/include/timeops.h
+++ b/include/timeops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * timeops.h
- * Operators for time types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file timeops.h
+ * Operators for time types.
+ */
+
 #ifndef __TIMEOPS_H__
 #define __TIMEOPS_H__
 
diff --git a/include/timestampset.h b/include/timestampset.h
index 16bf699cf9..0feef7a100 100644
--- a/include/timestampset.h
+++ b/include/timestampset.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * timestampset.h
- * Basic functions for set of timestamps.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file timestampset.h
+ * Basic functions for set of (distinct) timestamps.
+ */
+
 #ifndef __TIMESTAMPSET_H__
 #define __TIMESTAMPSET_H__
 
@@ -66,6 +68,7 @@ extern Datum timestampset_to_period(PG_FUNCTION_ARGS);
 /* Accessor functions */
 
 extern Datum timestampset_mem_size(PG_FUNCTION_ARGS);
+extern Datum timestampset_timespan(PG_FUNCTION_ARGS);
 extern Datum timestampset_num_timestamps(PG_FUNCTION_ARGS);
 extern Datum timestampset_start_timestamp(PG_FUNCTION_ARGS);
 extern Datum timestampset_end_timestamp(PG_FUNCTION_ARGS);
diff --git a/include/timetypes.h b/include/timetypes.h
index 7a425d55fb..3ad8c77c18 100644
--- a/include/timetypes.h
+++ b/include/timetypes.h
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * timetypes.h
- * Functions for time types based on timestamptz, that is,
- * timestampset, period, periodset
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,15 +24,15 @@
  *
  *****************************************************************************/
 
- /** @file timetypes.h
- * Functions for time types based on `timestamptz`, that is,
- * `timestampset`, `period`, and `periodset`.
+/** @file timetypes.h
+ * Functions for time types based on `TimestampTz`, that is,
+ * `TimestampSet`, `Period`, and `PeriodSet`.
  *
  * The `Period` type is a specialized version of the `RangeType` in PostgreSQL.
  * It is considerably more efficient, in particular because it is a
  * fix-length type, it has finite bounds, and do not allow empty periods.
- * The `TimestampSet` type represents a set of disjoint `timestamptz`.
- * The `PeriodSet` type represents a set of disjoint periods.
+ * The `TimestampSet` type represents sets of disjoint `TimestampTz`.
+ * The `PeriodSet` type represents sets of disjoint `Period` values.
  */
  
 #ifndef __TIMETYPES_H__
diff --git a/include/tinstant.h b/include/tinstant.h
index 608ed2344c..33c67eb0fe 100644
--- a/include/tinstant.h
+++ b/include/tinstant.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tinstant.h
- * Basic functions for temporal instants.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tinstant.h
+ * Basic functions for temporal instants.
+ */
+
 #ifndef __TINSTANT_H__
 #define __TINSTANT_H__
 
diff --git a/include/tinstantset.h b/include/tinstantset.h
index 0aa6861c82..958a5a239a 100644
--- a/include/tinstantset.h
+++ b/include/tinstantset.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tinstantset.h
- * Basic functions for temporal instant sets.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tinstantset.h
+ * Basic functions for temporal instant sets.
+ */
+
 #ifndef __TINSTANTSET_H__
 #define __TINSTANTSET_H__
 
@@ -41,8 +43,8 @@
 
 extern TInstant *tinstantset_inst_n(const TInstantSet *ti, int index);
 extern bool tinstantset_find_timestamp(const TInstantSet *ti, TimestampTz t, int *pos);
-extern TInstantSet *tinstantset_make(TInstant **instants, int count);
-extern TInstantSet *tinstantset_make_free(TInstant **instants, int count);
+extern TInstantSet *tinstantset_make(TInstant **instants, int count, bool merge);
+extern TInstantSet *tinstantset_make_free(TInstant **instants, int count, bool merge);
 extern TInstantSet *tinstantset_copy(const TInstantSet *ti);
 
 /* Intersection functions */
@@ -93,6 +95,7 @@ extern void tinstantset_bbox(void *box, const TInstantSet *ti);
 extern Datum tinstantset_min_value(const TInstantSet *ti);
 extern Datum tinstantset_max_value(const TInstantSet *ti);
 extern void tinstantset_period(Period *p, const TInstantSet *ti);
+extern Datum tinstantset_timespan(const TInstantSet *ti);
 extern TInstant **tinstantset_instants(const TInstantSet *ti);
 extern ArrayType *tinstantset_instants_array(const TInstantSet *ti);
 extern TimestampTz tinstantset_start_timestamp(const TInstantSet *ti);
diff --git a/include/tnumber_distance.h b/include/tnumber_distance.h
index 322e371e18..8de1d96442 100644
--- a/include/tnumber_distance.h
+++ b/include/tnumber_distance.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_distance.h
- * Distance functions for temporal numbers.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_distance.h
+ * Distance functions for temporal numbers.
+ */
+
 #ifndef __TNUMBER_DISTANCE_H__
 #define __TNUMBER_DISTANCE_H__
 
diff --git a/include/tnumber_gist.h b/include/tnumber_gist.h
index e57631243a..58a330b74b 100644
--- a/include/tnumber_gist.h
+++ b/include/tnumber_gist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_gist.c
- * R-tree GiST index for temporal integers and temporal floats
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_gist.c
+ * R-tree GiST index for temporal integers and temporal floats
+ */
+
 #ifndef __TNUMBER_GIST_H__
 #define __TNUMBER_GIST_H__
 
diff --git a/include/tnumber_mathfuncs.h b/include/tnumber_mathfuncs.h
index 28a37fca8a..2e57cbd59c 100644
--- a/include/tnumber_mathfuncs.h
+++ b/include/tnumber_mathfuncs.h
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_mathfuncs.c
- * Temporal mathematical operators (+, -, *, /) and functions (round,
- * degrees).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,6 +24,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_mathfuncs.c
+ * Temporal mathematical operators (+, -, *, /) and functions (round,
+ * degrees).
+ */
+
 #ifndef __TEMPORAL_MATHFUNCS_H__
 #define __TEMPORAL_MATHFUNCS_H__
 
diff --git a/include/tnumber_selfuncs.h b/include/tnumber_selfuncs.h
index 27eb735776..acd5bbbbe9 100644
--- a/include/tnumber_selfuncs.h
+++ b/include/tnumber_selfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_selfuncs.h
- * Functions for selectivity estimation of operators on temporal number types
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_selfuncs.h
+ * Functions for selectivity estimation of operators on temporal number types
+ */
+
 #ifndef __TNUMBER_SELFUNCS_H__
 #define __TNUMBER_SELFUNCS_H__
 
diff --git a/include/tnumber_spgist.h b/include/tnumber_spgist.h
index b9f9189658..164747a9e7 100644
--- a/include/tnumber_spgist.h
+++ b/include/tnumber_spgist.h
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_spgist.c
- * SP-GiST implementation of 4-dimensional quad tree over temporal
- * integers and floats.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,6 +24,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_spgist.c
+ * SP-GiST implementation of 4-dimensional quad tree over temporal
+ * integers and floats.
+ */
+
 #ifndef __TNUMBER_SPGIST_H__
 #define __TNUMBER_SPGIST_H__
 
diff --git a/include/tsequence.h b/include/tsequence.h
index 7014856c4f..69b0d28730 100644
--- a/include/tsequence.h
+++ b/include/tsequence.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tsequence.h
- * Basic functions for temporal sequences.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tsequence.h
+ * Basic functions for temporal sequences.
+ */
+
 #ifndef __TSEQUENCE_H__
 #define __TSEQUENCE_H__
 
@@ -94,7 +96,6 @@ extern Datum tsequence_from_base(PG_FUNCTION_ARGS);
 
 /* Append and merge functions */
 
-extern TSequence *tsequence_join(const TSequence *seq1, const TSequence *seq2, bool last, bool first);
 extern Temporal *tsequence_append_tinstant(const TSequence *seq, const TInstant *inst);
 extern Temporal *tsequence_merge(const TSequence *seq1, const TSequence *seq2);
 extern TSequence **tsequence_merge_array1(TSequence **sequences, int count, int *totalcount);
@@ -126,7 +127,7 @@ extern TInstant *tsequence_min_instant(const TSequence *seq);
 extern Datum tsequence_min_value(const TSequence *seq);
 extern Datum tsequence_max_value(const TSequence *seq);
 extern void tsequence_period(Period *p, const TSequence *seq);
-extern Datum tsequence_timespan(const TSequence *seq);
+extern Datum tsequence_duration(const TSequence *seq);
 extern TInstant **tsequence_instants(const TSequence *seq);
 extern ArrayType *tsequence_instants_array(const TSequence *seq);
 extern TimestampTz tsequence_start_timestamp(const TSequence *seq);
diff --git a/include/tsequenceset.h b/include/tsequenceset.h
index 5990216b90..913de1cee7 100644
--- a/include/tsequenceset.h
+++ b/include/tsequenceset.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tsequenceset.h
- * Basic functions for temporal sequence sets.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tsequenceset.h
+ * Basic functions for temporal sequence sets.
+ */
+
 #ifndef __TSEQUENCESET_H__
 #define __TSEQUENCESET_H__
 
@@ -119,6 +121,7 @@ extern Datum tsequenceset_min_value(const TSequenceSet *ts);
 extern Datum tsequenceset_max_value(const TSequenceSet *ts);
 extern PeriodSet *tsequenceset_get_time(const TSequenceSet *ts);
 extern Datum tsequenceset_timespan(const TSequenceSet *ts);
+extern Datum tsequenceset_duration(const TSequenceSet *ts);
 extern void tsequenceset_period(Period *p, const TSequenceSet *ts);
 extern TSequence **tsequenceset_sequences(const TSequenceSet *ts);
 extern ArrayType *tsequenceset_sequences_array(const TSequenceSet *ts);
diff --git a/include/ttext_textfuncs.h b/include/ttext_textfuncs.h
index 3101b178e7..ec3c7477b7 100644
--- a/include/ttext_textfuncs.h
+++ b/include/ttext_textfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * ttext_textfuncs.h
- * Text functions (textcat, lower, upper).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file ttext_textfuncs.h
+ * Temporal text functions: `textcat`, `lower`, `upper`.
+ */
+
 #ifndef __TTEXT_TEXTFUNCS_H__
 #define __TTEXT_TEXTFUNCS_H__
 
diff --git a/point/include/geography_funcs.h b/point/include/geography_funcs.h
index 6773b83921..3b159afdce 100644
--- a/point/include/geography_funcs.h
+++ b/point/include/geography_funcs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * geography_functions.h
- * Spatial functions for PostGIS geography.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file geography_funcs.h
+ * Spatial functions for PostGIS geography.
+ */
+
 #ifndef __GEOGRAPHY_FUNCTIONS_H__
 #define __GEOGRAPHY_FUNCTIONS_H__
 
diff --git a/point/include/postgis.h b/point/include/postgis.h
index 6e24278c3a..054d9ee8f5 100644
--- a/point/include/postgis.h
+++ b/point/include/postgis.h
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * postgis.h
- * PostGIS definitions that are needed in the extension but are not exported
- * in PostGIS headers
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,6 +24,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file postgis.h
+ * PostGIS definitions that are needed in MobilityDB but are not exported
+ * in PostGIS headers
+ */
+
 #ifndef __POSTGIS_H__
 #define __POSTGIS_H__
 
diff --git a/point/include/projection_gk.h b/point/include/projection_gk.h
index 63aa54b4c5..a1bcb2d507 100644
--- a/point/include/projection_gk.h
+++ b/point/include/projection_gk.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * projection_gk.h
- * Implementation of the Gauss Krueger projection that is used in Secondo
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file projection_gk.h
+ * Implementation of the Gauss-Krueger projection that is used in Secondo
+ */
+
 #ifndef __PROJECTION_GK_H__
 #define __PROJECTION_GK_H__
 
diff --git a/point/include/stbox.h b/point/include/stbox.h
index 0557ea25f5..cc924957ee 100644
--- a/point/include/stbox.h
+++ b/point/include/stbox.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * stbox.h
- * Functions for spatiotemporal bounding boxes.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file stbox.h
+ * Functions for spatiotemporal bounding boxes.
+ */
+
 #ifndef __STBOX_H__
 #define __STBOX_H__
 
diff --git a/point/include/tpoint.h b/point/include/tpoint.h
index dbd2d8d366..74b1bbb9c2 100644
--- a/point/include/tpoint.h
+++ b/point/include/tpoint.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint.h
- * Functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint.h
+ * Functions for temporal points.
+ */
+
 #ifndef __TPOINT_H__
 #define __TPOINT_H__
 
diff --git a/point/include/tpoint_aggfuncs.h b/point/include/tpoint_aggfuncs.h
index 14ecb3765e..4141315641 100644
--- a/point/include/tpoint_aggfuncs.h
+++ b/point/include/tpoint_aggfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_aggfuncs.h
- * Aggregate functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_aggfuncs.h
+ * Aggregate functions for temporal points.
+ */
+
 #ifndef __TPOINT_AGGFUNCS_H__
 #define __TPOINT_AGGFUNCS_H__
 
diff --git a/point/include/tpoint_analytics.h b/point/include/tpoint_analytics.h
index 9a37e291ab..e4709b152e 100644
--- a/point/include/tpoint_analytics.h
+++ b/point/include/tpoint_analytics.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_analytics.h
- * Analytics functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_analytics.h
+ * Analytics functions for temporal points.
+ */
+
 #ifndef __TPOINT_ANALYTICS_H__
 #define __TPOINT_ANALYTICS_H__
 
diff --git a/point/include/tpoint_analyze.h b/point/include/tpoint_analyze.h
index aab93ef33a..b5102d075a 100644
--- a/point/include/tpoint_analyze.h
+++ b/point/include/tpoint_analyze.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_analyze.h
- * Functions for gathering statistics from temporal point columns
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_analyze.h
+ * Functions for gathering statistics from temporal point columns
+ */
+
 #ifndef __TPOINT_ANALYZE_H__
 #define __TPOINT_ANALYZE_H__
 
diff --git a/point/include/tpoint_boxops.h b/point/include/tpoint_boxops.h
index 627bfd977c..eec076722e 100644
--- a/point/include/tpoint_boxops.h
+++ b/point/include/tpoint_boxops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_boxops.h
- * Bounding box operators for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_boxops.h
+ * Bounding box operators for temporal points.
+ */
+
 #ifndef __TPOINT_BOXOPS_H__
 #define __TPOINT_BOXOPS_H__
 
diff --git a/point/include/tpoint_datagen.h b/point/include/tpoint_datagen.h
index 56baf846a9..03415049c4 100644
--- a/point/include/tpoint_datagen.h
+++ b/point/include/tpoint_datagen.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_datagen.h
- * Data generator for MobilityDB.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_datagen.h
+ * Data generator for MobilityDB.
+ */
+
 #ifndef __TPOINT_DATAGEN_H__
 #define __TPOINT_DATAGEN_H__
 
diff --git a/point/include/tpoint_distance.h b/point/include/tpoint_distance.h
index b77d535757..61a2c4bb70 100644
--- a/point/include/tpoint_distance.h
+++ b/point/include/tpoint_distance.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_distance.h
- * Distance functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_distance.h
+ * Distance functions for temporal points.
+ */
+
 #ifndef __TPOINT_DISTANCE_H__
 #define __TPOINT_DISTANCE_H__
 
diff --git a/point/include/tpoint_gist.h b/point/include/tpoint_gist.h
index 9dbf2a3908..8971beb07b 100644
--- a/point/include/tpoint_gist.h
+++ b/point/include/tpoint_gist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_gist.c
- * R-tree GiST index for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_gist.c
+ * R-tree GiST index for temporal points.
+ */
+
 #ifndef __TPOINT_GIST_H__
 #define __TPOINT_GIST_H__
 
diff --git a/point/include/tpoint_in.h b/point/include/tpoint_in.h
index 25e19e4b0e..ad3fc5f31e 100644
--- a/point/include/tpoint_in.h
+++ b/point/include/tpoint_in.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_in.h
- * Input of temporal points in WKT, EWKT and MF-JSON format
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_in.h
+ * Input of temporal points in WKT, EWKT and MF-JSON format
+ */
+
 #ifndef __TPOINT_IN_H__
 #define __TPOINT_IN_H__
 
diff --git a/point/include/tpoint_out.h b/point/include/tpoint_out.h
index 79357a2bd9..5c07ccafed 100644
--- a/point/include/tpoint_out.h
+++ b/point/include/tpoint_out.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_out.h
- * Output of temporal points in WKT, EWKT and MF-JSON format
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_out.h
+ * Output of temporal points in WKT, EWKT and MF-JSON format
+ */
+
 #ifndef __TPOINT_OUT_H__
 #define __TPOINT_OUT_H__
 
diff --git a/point/include/tpoint_posops.h b/point/include/tpoint_posops.h
index 8bc7dc31c2..b7a0788042 100644
--- a/point/include/tpoint_posops.h
+++ b/point/include/tpoint_posops.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_posops.h
- * Relative position operators for temporal geometry points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_posops.h
+ * Relative position operators for temporal geometry points.
+ */
+
 #ifndef __TPOINT_POSOPS_H__
 #define __TPOINT_POSOPS_H__
 
diff --git a/point/include/tpoint_selfuncs.h b/point/include/tpoint_selfuncs.h
index c91ad1bf3a..7b9cd2c657 100644
--- a/point/include/tpoint_selfuncs.h
+++ b/point/include/tpoint_selfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_selfuncs.h
- * Selectivity functions for the temporal point types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,9 +26,9 @@
 
 /**
  * @file tpoint_selfuncs.c
- * Selectivity functions for the temporal point types.
+ * Selectivity functions for temporal point types.
  *
- * Most definitions in this file come from PostGIS file 
+ * Most definitions in this file come from the PostGIS file 
  * `gserialized_estimate.c`
  */
 
diff --git a/point/include/tpoint_spatialfuncs.h b/point/include/tpoint_spatialfuncs.h
index 20f7f57305..d567e368aa 100644
--- a/point/include/tpoint_spatialfuncs.h
+++ b/point/include/tpoint_spatialfuncs.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_spatialfuncs.h
- * Spatial functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_spatialfuncs.h
+ * Spatial functions for temporal points.
+ */
+
 #ifndef __TPOINT_SPATIALFUNCS_H__
 #define __TPOINT_SPATIALFUNCS_H__
 
diff --git a/point/include/tpoint_spatialrels.h b/point/include/tpoint_spatialrels.h
index cc98a9466e..ec02503858 100644
--- a/point/include/tpoint_spatialrels.h
+++ b/point/include/tpoint_spatialrels.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_spatialrels.h
- * Spatial relationships for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_spatialrels.h
+ * Spatial relationships for temporal points.
+ */
+
 #ifndef __TPOINT_SPATIALRELS_H__
 #define __TPOINT_SPATIALRELS_H__
 
diff --git a/point/include/tpoint_spgist.h b/point/include/tpoint_spgist.h
index f0415c2ba8..8acb10fe78 100644
--- a/point/include/tpoint_spgist.h
+++ b/point/include/tpoint_spgist.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_spgist.h
- * SP-GiST implementation of 8-dimensional oct-tree over temporal points
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_spgist.h
+ * SP-GiST implementation of 8-dimensional oct-tree over temporal points
+ */
+
 #ifndef __TPOINT_SPGIST_H__
 #define __TPOINT_SPGIST_H__
 
diff --git a/point/include/tpoint_tempspatialrels.h b/point/include/tpoint_tempspatialrels.h
index 9d684ebfde..c8a9ac14d7 100644
--- a/point/include/tpoint_tempspatialrels.h
+++ b/point/include/tpoint_tempspatialrels.h
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_tempspatialrels.h
- * Temporal spatial relationships for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_tempspatialrels.h
+ * Temporal spatial relationships for temporal points.
+ */
+
 #ifndef __TPOINT_TEMPSPATIALRELS_H__
 #define __TPOINT_TEMPSPATIALRELS_H__
 
diff --git a/point/src/geography_functions.c b/point/src/geography_functions.c
index 83c7de91fc..ba3b025a9a 100644
--- a/point/src/geography_functions.c
+++ b/point/src/geography_functions.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * geography_functions.c
- * Spatial functions for PostGIS geography.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -26,6 +23,7 @@
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. 
  *
  *****************************************************************************/
+
 /**
  * @file geography_functions.c
  * Spatial functions for PostGIS geography.
diff --git a/point/src/projection_gk.c b/point/src/projection_gk.c
index 261c3f4755..5ce374bb0c 100644
--- a/point/src/projection_gk.c
+++ b/point/src/projection_gk.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * projection_gk.c
- * Implementation of the Gauss Krueger projection that is used in Secondo
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -26,9 +23,10 @@
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. 
  *
  *****************************************************************************/
+
 /**
  * @file projection_gk.c
- *    Implementation of the Gauss Krueger projection that is used in Secondo
+ * Implementation of the Gauss-Krueger projection that is used in Secondo
  *
  * This projection does not correspond to any standard projection in
  * http://www.epsg.org/. This projection is provided to enable the comparison
diff --git a/point/src/sql/51_tpoint.in.sql b/point/src/sql/51_tpoint.in.sql
index 5a4a370e00..f27b99e574 100644
--- a/point/src/sql/51_tpoint.in.sql
+++ b/point/src/sql/51_tpoint.in.sql
@@ -398,6 +398,15 @@ CREATE FUNCTION timespan(tgeogpoint)
   AS 'MODULE_PATHNAME', 'temporal_timespan'
   LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION duration(tgeompoint)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'temporal_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+CREATE FUNCTION duration(tgeogpoint)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'temporal_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION numInstants(tgeompoint)
   RETURNS integer
   AS 'MODULE_PATHNAME', 'temporal_num_instants'
diff --git a/point/src/stbox.c b/point/src/stbox.c
index d622f98735..41382142b2 100644
--- a/point/src/stbox.c
+++ b/point/src/stbox.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * stbox.c
- * Functions for spatiotemporal bounding boxes.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file stbox.c
+ * Functions for spatiotemporal bounding boxes.
+ */
+
 #include "stbox.h"
 
 #include <assert.h>
diff --git a/point/src/tpoint.c b/point/src/tpoint.c
index 443c7810fd..638473969d 100644
--- a/point/src/tpoint.c
+++ b/point/src/tpoint.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint.c
- * Basic functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint.c
+ * Basic functions for temporal points.
+ */
+
 #include "tpoint.h"
 
 #include <utils/builtins.h>
diff --git a/point/src/tpoint_aggfuncs.c b/point/src/tpoint_aggfuncs.c
index c3ab58a6a9..509906c1d7 100644
--- a/point/src/tpoint_aggfuncs.c
+++ b/point/src/tpoint_aggfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_aggfuncs.c
- * Aggregate functions for temporal points.
  *
  * Copyright (c) 2020, Université libre de Bruxelles and MobilityDB
  * contributors
@@ -24,6 +21,7 @@
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. 
  *
  *****************************************************************************/
+
 /**
  * @file tpoint_aggfuncs.c
  *  Aggregate functions for temporal points.
@@ -420,7 +418,7 @@ tpointinst_tcentroid_finalfn(TInstant **instants, int count, int srid)
     newinstants[i] = tinstant_make(value, inst->t, type_oid(T_GEOMETRY));
     pfree(DatumGetPointer(value));
   }
-  return tinstantset_make_free(newinstants, count);
+  return tinstantset_make_free(newinstants, count, MERGE_NO);
 }
 
 /**
diff --git a/point/src/tpoint_analytics.c b/point/src/tpoint_analytics.c
index 11c06c5d94..4e0d5e784d 100644
--- a/point/src/tpoint_analytics.c
+++ b/point/src/tpoint_analytics.c
@@ -1,7 +1,4 @@
 /***********************************************************************
- *
- * tpoint_analytics.c
- * Analytic functions for temporal points and temporal floats.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_analytics.c
+ * Analytic functions for temporal points and temporal floats.
+ */
+
 #include "tpoint_analytics.h"
 
 #include <assert.h>
@@ -468,7 +470,7 @@ geo_to_tpointinstset(GSERIALIZED *gs)
     instants[i] = trajpoint_to_tpointinst((LWPOINT *)lwcoll->geoms[i]);
   lwgeom_free(lwgeom);
 
-  return tinstantset_make_free(instants, npoints);
+  return tinstantset_make_free(instants, npoints, MERGE_NO);
 }
 
 /**
diff --git a/point/src/tpoint_analyze.c b/point/src/tpoint_analyze.c
index c7f6d2475d..42f776b5fb 100644
--- a/point/src/tpoint_analyze.c
+++ b/point/src/tpoint_analyze.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_analyze.c
- * Functions for gathering statistics from temporal point columns
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/point/src/tpoint_boxops.c b/point/src/tpoint_boxops.c
index 142dac4f4c..6e6a1ed633 100644
--- a/point/src/tpoint_boxops.c
+++ b/point/src/tpoint_boxops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_boxops.c
- * Bounding box operators for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,7 +26,7 @@
 
 /**
  * @file tpoint_boxops.c
- *    Bounding box operators for temporal points.
+ * Bounding box operators for temporal points.
  *
  * These operators test the bounding boxes of temporal points, which are an
  * `STBOX`, where the *x*, *y*, and optional *z* coordinates are for the space 
diff --git a/point/src/tpoint_datagen.c b/point/src/tpoint_datagen.c
index 5beac4551a..45bb10b168 100644
--- a/point/src/tpoint_datagen.c
+++ b/point/src/tpoint_datagen.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_datagen.c
- * Data generator for MobilityDB.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,14 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_datagen.c
+ * Data generator for MobilityDB.
+ *
+ * These functions are used in particular for the BerlinMOD data generator
+ * https://github.com/MobilityDB/MobilityDB-BerlinMOD
+ */
+
 #include "tpoint_datagen.h"
 
 #include <access/htup_details.h>
diff --git a/point/src/tpoint_distance.c b/point/src/tpoint_distance.c
index 0e7f52bb4a..85dc0c91a5 100644
--- a/point/src/tpoint_distance.c
+++ b/point/src/tpoint_distance.c
@@ -1,7 +1,4 @@
 /***********************************************************************
- *
- * tpoint_distance.c
- * Distance functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_distance.c
+ * Distance functions for temporal points.
+ */
+
 #include "tpoint_distance.h"
 
 #include <assert.h>
diff --git a/point/src/tpoint_gist.c b/point/src/tpoint_gist.c
index b8b2cd00e4..6bba2ed47b 100644
--- a/point/src/tpoint_gist.c
+++ b/point/src/tpoint_gist.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_gist.c
- * R-tree GiST index for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_gist.c
+ * R-tree GiST index for temporal points.
+ */
+
 #include "tpoint_gist.h"
 
 #include <assert.h>
diff --git a/point/src/tpoint_in.c b/point/src/tpoint_in.c
index 44de8816e9..e066e80cfa 100644
--- a/point/src/tpoint_in.c
+++ b/point/src/tpoint_in.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_in.c
- * Input of temporal points in WKT, EWKT and MF-JSON format
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_in.c
+ * Input of temporal points in WKT, EWKT and MF-JSON format
+ */
+
 #include "tpoint_in.h"
 
 #include <assert.h>
@@ -294,7 +296,7 @@ tpointinstset_from_mfjson(json_object *mfjson, int srid)
 {
   int count;
   TInstant **instants = tpointinstarr_from_mfjson(mfjson, srid, &count);
-  return tinstantset_make_free(instants, count);
+  return tinstantset_make_free(instants, count, MERGE_NO);
 }
 
 /**
@@ -727,7 +729,7 @@ tpointinstset_from_wkb_state(wkb_parse_state *s)
   wkb_parse_state_check(s, size);
   /* Parse the instants */
   TInstant **instants = tpointinstarr_from_wkb_state(s, count);
-  return tinstantset_make_free(instants, count);
+  return tinstantset_make_free(instants, count, MERGE_NO);
 }
 
 /**
diff --git a/point/src/tpoint_out.c b/point/src/tpoint_out.c
index 5aa256f340..817bcbd2b7 100644
--- a/point/src/tpoint_out.c
+++ b/point/src/tpoint_out.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_out.c
- * Output of temporal points in WKT, EWKT, WKB, EWKB, and MF-JSON format
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_out.c
+ * Output of temporal points in WKT, EWKT, WKB, EWKB, and MF-JSON format
+ */
+
 #include "tpoint_out.h"
 
 #include <assert.h>
diff --git a/point/src/tpoint_parser.c b/point/src/tpoint_parser.c
index 0bacf043ad..1ecbdafbe7 100644
--- a/point/src/tpoint_parser.c
+++ b/point/src/tpoint_parser.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_parser.c
- * Functions for parsing temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_parser.c
+ * Functions for parsing temporal points.
+ */
+
 #include "tpoint_parser.h"
 
 #include "temporaltypes.h"
@@ -292,7 +294,7 @@ tpointinstset_parse(char **str, Oid basetype, int *tpoint_srid)
     instants[i] = tpointinst_parse(str, basetype, false, true, tpoint_srid);
   }
   p_cbrace(str);
-  return tinstantset_make_free(instants, count);
+  return tinstantset_make_free(instants, count, MERGE_NO);
 }
 
 /**
diff --git a/point/src/tpoint_posops.c b/point/src/tpoint_posops.c
index bab4e74227..86eb645259 100644
--- a/point/src/tpoint_posops.c
+++ b/point/src/tpoint_posops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_posops.c
- * Relative position operators for temporal geometry points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -26,6 +23,7 @@
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. 
  *
  *****************************************************************************/
+
 /**
  * @file tpoint_posops.c
  * Relative position operators for temporal geometry points.
@@ -39,7 +37,8 @@
  * The following operators are defined for for the time dimension: `before`, 
  * `overbefore`,  `after`, `overafter`. For both temporal geometry and 
  * geography points the same operators are derived from the basic temporal 
- * types. In this file they are defined when one of the arguments is a stbox.
+ * types. In this file they are defined when one of the arguments is an 
+ * `STBOX`.
  */
  
 #include "tpoint_posops.h"
diff --git a/point/src/tpoint_selfuncs.c b/point/src/tpoint_selfuncs.c
index a8040ab6d3..659c9ec28f 100644
--- a/point/src/tpoint_selfuncs.c
+++ b/point/src/tpoint_selfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_selfuncs.c
- * Functions for selectivity estimation of operators on temporal points
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_selfuncs.c
+ * Functions for selectivity estimation of operators on temporal points
+ */
+
 #include "tpoint_selfuncs.h"
 
 #include <assert.h>
diff --git a/point/src/tpoint_spatialfuncs.c b/point/src/tpoint_spatialfuncs.c
index a93711a255..17e164bc7f 100644
--- a/point/src/tpoint_spatialfuncs.c
+++ b/point/src/tpoint_spatialfuncs.c
@@ -1,7 +1,4 @@
 /***********************************************************************
- *
- * tpoint_spatialfuncs.c
- * Spatial functions for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tpoint_spatialfuncs.c
+ * Spatial functions for temporal points.
+ */
+
 #include "tpoint_spatialfuncs.h"
 
 #include <assert.h>
@@ -1617,7 +1619,7 @@ tpointinstset_transform(const TInstantSet *ti, Datum srid)
   if (ti->count == 1)
   {
     inst = tpointinst_transform(tinstantset_inst_n(ti, 0), srid);
-    TInstantSet *result = tinstantset_make(&inst, 1);
+    TInstantSet *result = tinstantset_make(&inst, 1, MERGE_NO);
     pfree(inst);
     return result;
   }
@@ -1649,7 +1651,7 @@ tpointinstset_transform(const TInstantSet *ti, Datum srid)
   POSTGIS_FREE_IF_COPY_P(gs, DatumGetPointer(gs));
   lwmpoint_free(lwmpoint);
 
-  return tinstantset_make_free(instants, ti->count);
+  return tinstantset_make_free(instants, ti->count, MERGE_NO);
 }
 
 /**
@@ -1855,7 +1857,7 @@ tpointinstset_convert_tgeom_tgeog(const TInstantSet *ti, bool oper)
     pfree(DatumGetPointer(point));
   }
   lwmpoint_free(lwmpoint);
-  return tinstantset_make_free(instants, ti->count);
+  return tinstantset_make_free(instants, ti->count, MERGE_NO);
 }
 
 /**
@@ -2102,7 +2104,7 @@ tpointinstset_cumulative_length(const TInstantSet *ti)
     TInstant *inst = tinstantset_inst_n(ti, i);
     instants[i] = tinstant_make(length, inst->t, FLOAT8OID);
   }
-  return tinstantset_make_free(instants, ti->count);
+  return tinstantset_make_free(instants, ti->count, MERGE_NO);
 }
 
 /**
@@ -2356,11 +2358,11 @@ tgeompointi_twcentroid(const TInstantSet *ti)
       instantsz[i] = tinstant_make(Float8GetDatum(point.z), inst->t,
         FLOAT8OID);
   }
-  TInstantSet *tix = tinstantset_make_free(instantsx, ti->count);
-  TInstantSet *tiy = tinstantset_make_free(instantsy, ti->count);
+  TInstantSet *tix = tinstantset_make_free(instantsx, ti->count, MERGE_NO);
+  TInstantSet *tiy = tinstantset_make_free(instantsy, ti->count, MERGE_NO);
   TInstantSet *tiz = NULL; /* keep compiler quiet */
   if (hasz)
-    tiz = tinstantset_make_free(instantsz, ti->count);
+    tiz = tinstantset_make_free(instantsz, ti->count, MERGE_NO);
   double avgx = tnumberinstset_twavg(tix);
   double avgy = tnumberinstset_twavg(tiy);
   double avgz;
@@ -2857,7 +2859,7 @@ tgeompointseq_find_intersections(const TSequence *seq, int *count)
 /**
  * Determine whether a temporal point is self-intersecting
  *
- * @param[in] seq Temporal point
+ * @param[in] ti Temporal point
  */
 static int
 tgeompointi_is_simple(const TInstantSet *ti)
@@ -3033,12 +3035,12 @@ tgeompointi_make_simple1(TInstantSet **result, const TInstantSet *ti)
     }
     else
     {
-      result[count++] = tinstantset_make(instants, k);
+      result[count++] = tinstantset_make(instants, k, MERGE_NO);
       points[0] = p3dz;
       k = 1;
     }
   }
-  result[count++] = tinstantset_make(instants, k);
+  result[count++] = tinstantset_make(instants, k, MERGE_NO);
   pfree(points);
   return count;
 }
@@ -3236,7 +3238,7 @@ tpointinstset_restrict_geometry(const TInstantSet *ti, Datum geom, bool atfunc)
   }
   TInstantSet *result = NULL;
   if (k != 0)
-    result = tinstantset_make(instants, k);
+    result = tinstantset_make(instants, k, MERGE_NO);
   /* We cannot pfree the instants in the array */
   pfree(instants);
   return result;
@@ -3246,7 +3248,7 @@ tpointinstset_restrict_geometry(const TInstantSet *ti, Datum geom, bool atfunc)
  * Restricts the temporal sequence point with step interpolation to the geometry
  *
  * @param[in] seq Temporal point
- * @param[in] geom Geometry
+ * @param[in] gsinter Intersection of the temporal point and the geometry
  * @param[out] count Number of elements in the resulting array
  * @pre The temporal point is simple (that is, not self-intersecting)
  */
@@ -3303,7 +3305,8 @@ tpointseq_step_at_geometry(const TSequence *seq, GSERIALIZED *gsinter, int *coun
  * Restricts the temporal sequence point with linear interpolation to the geometry
  *
  * @param[in] seq Temporal point
- * @param[in] geom Geometry
+ * @param[in] traj Trajectory of the temporal point
+ * @param[in] gsinter Intersection of the temporal point and the geometry
  * @param[out] count Number of elements in the resulting array
  * @pre The temporal point is simple (that is, not self-intersecting)
  */
diff --git a/point/src/tpoint_spatialrels.c b/point/src/tpoint_spatialrels.c
index 598df262a2..0c2da10253 100644
--- a/point/src/tpoint_spatialrels.c
+++ b/point/src/tpoint_spatialrels.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_spatialrels.c
- * Spatial relationships for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,6 +26,8 @@
 
 /**
  * @file tpoint_spatialrels.c
+ * Spatial relationships for temporal points.
+ *
  * These relationships project the time dimension and return a Boolean.
  * They are thus defined with the "at any instant" semantics, that is, the
  * traditional spatial function is applied to the union of all values taken
diff --git a/point/src/tpoint_spgist.c b/point/src/tpoint_spgist.c
index 73ad056332..645f6a285f 100644
--- a/point/src/tpoint_spgist.c
+++ b/point/src/tpoint_spgist.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_spgist.c
- * SP-GiST implementation of 8-dimensional oct-tree over temporal points
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,7 +26,9 @@
 
 /**
  * @file tnumber_spgist.c
- * This module provides SP-GiST implementation for boxes using oct tree
+ * SP-GiST implementation of 8-dimensional oct-tree over temporal points
+ *
+ * This module provides SP-GiST implementation for boxes using an oct-tree
  * analogy in 8-dimensional space.  SP-GiST doesn't allow indexing of
  * overlapping objects.  We are making 4D objects never-overlapping in
  * 8D space.  This technique has some benefits compared to traditional
diff --git a/point/src/tpoint_tempspatialrels.c b/point/src/tpoint_tempspatialrels.c
index bc210c656d..79bdbd2252 100644
--- a/point/src/tpoint_tempspatialrels.c
+++ b/point/src/tpoint_tempspatialrels.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tpoint_tempspatialrels.c
- * Temporal spatial relationships for temporal points.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/point/test/expected/50_stbox.test.out b/point/test/expected/50_stbox.test.out
index eed5b0ca86..b410fedf24 100644
--- a/point/test/expected/50_stbox.test.out
+++ b/point/test/expected/50_stbox.test.out
@@ -86,11 +86,11 @@ ERROR:  Could not parse STBOX: Missing opening parenthesis
 LINE 1: SELECT stbox 'stbox(1, 2, 3)';
                      ^
 SELECT stbox 'stbox((AA, 2, 3))';
-ERROR:  Could not parse STBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT stbox 'stbox((AA, 2, 3))';
                      ^
 SELECT stbox 'stbox((1, AA, 3))';
-ERROR:  Could not parse STBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT stbox 'stbox((1, AA, 3))';
                      ^
 SELECT stbox 'stbox((,),(,))';
@@ -98,7 +98,7 @@ ERROR:  Could not parse STBOX
 LINE 1: SELECT stbox 'stbox((,),(,))';
                      ^
 SELECT stbox 'stbox z((1, 2, AA))';
-ERROR:  Could not parse STBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT stbox 'stbox z((1, 2, AA))';
                      ^
 SELECT stbox 'stbox t((1, 2, AA))';
@@ -114,15 +114,15 @@ ERROR:  Could not parse STBOX: Missing opening parenthesis
 LINE 1: SELECT stbox 'stbox t((1, 2, 2001-01-03))';
                      ^
 SELECT stbox 'stbox t((1, 2, 2001-01-03),()';
-ERROR:  Could not parse STBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT stbox 'stbox t((1, 2, 2001-01-03),()';
                      ^
 SELECT stbox 'stbox t((1, 2, 2001-01-03),(1)';
-ERROR:  Could not parse STBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT stbox 'stbox t((1, 2, 2001-01-03),(1)';
                      ^
 SELECT stbox 'stbox z((1, 2, 3),(1,2)';
-ERROR:  Could not parse STBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT stbox 'stbox z((1, 2, 3),(1,2)';
                      ^
 SELECT stbox 'stbox t((1, 2, 2001-01-03),(1,2)';
@@ -326,7 +326,7 @@ SELECT (geometry 'Polygon((1 1 1,1 2 2,2 2 2,2 1 1,1 1 1))'::box3d)::stbox;
  STBOX Z((1,1,1),(2,2,2))
 (1 row)
 
-SELECT MAX(timespan(b::period)) FROM tbl_stbox;
+SELECT MAX(duration(b::period)) FROM tbl_stbox;
    max    
 ----------
  00:10:00
diff --git a/point/test/expected/51_tpoint.test.out b/point/test/expected/51_tpoint.test.out
index b6c3a7c01b..61a2bf514c 100644
--- a/point/test/expected/51_tpoint.test.out
+++ b/point/test/expected/51_tpoint.test.out
@@ -1484,7 +1484,7 @@ ERROR:  The temporal points must be of the same dimensionality
 SELECT asText(appendInstant(tgeompoint '{Point(1 1)@2000-01-01, Point(2 2)@2000-01-02}', tgeompoint 'SRID=5676;Point(3 3)@2000-01-03'));
 ERROR:  The temporal points must be in the same SRID
 SELECT asText(appendInstant(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02]', tgeompoint 'Point(3 3)@2000-01-02'));
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-02 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-02 00:00:00+00
 SELECT asText(appendInstant(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02]', tgeompoint 'Point(3 3 3)@2000-01-03'));
 ERROR:  The temporal points must be of the same dimensionality
 SELECT asText(appendInstant(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02]', tgeompoint 'SRID=5676;Point(3 3)@2000-01-03'));
@@ -1613,19 +1613,19 @@ ERROR:  The temporal points must be of the same dimensionality
 SELECT merge(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', tgeompoint '[Point(2 2)@2000-01-02, Point(2 2)@2000-01-03, Point(1 1)@2000-01-04]');
 ERROR:  The temporal values cannot overlap on time: 2000-01-03 00:00:00+00, 2000-01-02 00:00:00+00
 SELECT merge(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', tgeompoint '[Point(2 2)@2000-01-03, Point(2 2)@2000-01-04, Point(1 1)@2000-01-05]');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(tgeompoint 'SRID=5676;[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', tgeompoint '[Point(1 1)@2000-01-03, Point(2 2)@2000-01-04, Point(1 1)@2000-01-05]');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', tgeompoint '[Point(1 1 1)@2000-01-03, Point(2 2 2)@2000-01-04, Point(1 1 1)@2000-01-05]');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', tgeompoint '{[Point(2 2)@2000-01-04, Point(2 2)@2000-01-05, Point(1 1)@2000-01-06],[Point(1 1)@2000-01-08, Point(1 1)@2000-01-09]}');
 ERROR:  The temporal values cannot overlap on time: 2000-01-05 00:00:00+00, 2000-01-04 00:00:00+00
 SELECT merge(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', tgeompoint '{[Point(2 2)@2000-01-05, Point(2 2)@2000-01-06, Point(1 1)@2000-01-07],[Point(1 1)@2000-01-08, Point(1 1)@2000-01-09]}');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT merge(tgeompoint 'SRID=5676;{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', tgeompoint '{[Point(1 1)@2000-01-05, Point(1 1)@2000-01-06],[Point(1 1)@2000-01-08, Point(1 1)@2000-01-09]}');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT merge(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', tgeompoint '{[Point(1 1 1)@2000-01-05, Point(1 1 1)@2000-01-06],[Point(1 1 1)@2000-01-08, Point(1 1 1)@2000-01-09]}');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT asText(merge(ARRAY[tgeompoint 'Point(1 1)@2000-01-01', 'Point(1 1)@2000-01-02']));
                                  astext                                 
 ------------------------------------------------------------------------
@@ -1703,19 +1703,19 @@ ERROR:  The temporal points must be of the same dimensionality
 SELECT merge(ARRAY [tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', '[Point(2 2)@2000-01-02, Point(2 2)@2000-01-03, Point(1 1)@2000-01-04]']);
 ERROR:  The temporal values cannot overlap on time: 2000-01-03 00:00:00+00, 2000-01-02 00:00:00+00
 SELECT merge(ARRAY [tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', '[Point(2 2)@2000-01-03, Point(2 2)@2000-01-04, Point(1 1)@2000-01-05]']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(ARRAY [tgeompoint 'SRID=5676;[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', '[Point(1 1)@2000-01-03, Point(2 2)@2000-01-04, Point(1 1)@2000-01-05]']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(ARRAY [tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]', '[Point(1 1 1)@2000-01-03, Point(2 2 2)@2000-01-04, Point(1 1 1)@2000-01-05]']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(ARRAY [tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', '{[Point(2 2)@2000-01-04, Point(2 2)@2000-01-05, Point(1 1)@2000-01-06],[Point(1 1)@2000-01-08, Point(1 1)@2000-01-09]}']);
 ERROR:  The temporal values cannot overlap on time: 2000-01-05 00:00:00+00, 2000-01-04 00:00:00+00
 SELECT merge(ARRAY [tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', '{[Point(2 2)@2000-01-05, Point(2 2)@2000-01-06, Point(1 1)@2000-01-07],[Point(1 1)@2000-01-08, Point(1 1)@2000-01-09]}']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT merge(ARRAY [tgeompoint 'SRID=5676;{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', '{[Point(1 1)@2000-01-05, Point(1 1)@2000-01-06],[Point(1 1)@2000-01-08, Point(1 1)@2000-01-09]}']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT merge(ARRAY [tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(1 1)@2000-01-04, Point(1 1)@2000-01-05]}', '{[Point(1 1 1)@2000-01-05, Point(1 1 1)@2000-01-06],[Point(1 1 1)@2000-01-08, Point(1 1 1)@2000-01-09]}']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT temporalType(tgeompoint 'Point(1 1)@2000-01-01');
  temporaltype 
 --------------
@@ -2135,7 +2135,7 @@ SELECT timespan(tgeompoint 'Point(1 1)@2000-01-01');
 SELECT timespan(tgeompoint '{Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03}');
  timespan 
 ----------
- 00:00:00
+ 2 days
 (1 row)
 
 SELECT timespan(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]');
@@ -2147,7 +2147,7 @@ SELECT timespan(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point
 SELECT timespan(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(3 3)@2000-01-04, Point(3 3)@2000-01-05]}');
  timespan 
 ----------
- 3 days
+ 4 days
 (1 row)
 
 SELECT timespan(tgeogpoint 'Point(1.5 1.5)@2000-01-01');
@@ -2159,7 +2159,7 @@ SELECT timespan(tgeogpoint 'Point(1.5 1.5)@2000-01-01');
 SELECT timespan(tgeogpoint '{Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03}');
  timespan 
 ----------
- 00:00:00
+ 2 days
 (1 row)
 
 SELECT timespan(tgeogpoint '[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03]');
@@ -2170,6 +2170,54 @@ SELECT timespan(tgeogpoint '[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-0
 
 SELECT timespan(tgeogpoint '{[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03],[Point(3.5 3.5)@2000-01-04, Point(3.5 3.5)@2000-01-05]}');
  timespan 
+----------
+ 4 days
+(1 row)
+
+SELECT duration(tgeompoint 'Point(1 1)@2000-01-01');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tgeompoint '{Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(3 3)@2000-01-04, Point(3 3)@2000-01-05]}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(tgeogpoint 'Point(1.5 1.5)@2000-01-01');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tgeogpoint '{Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tgeogpoint '[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(tgeogpoint '{[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03],[Point(3.5 3.5)@2000-01-04, Point(3.5 3.5)@2000-01-05]}');
+ duration 
 ----------
  3 days
 (1 row)
diff --git a/point/test/expected/51_tpoint_tbl.test.out b/point/test/expected/51_tpoint_tbl.test.out
index eeaa15e677..7ef4eec64a 100644
--- a/point/test/expected/51_tpoint_tbl.test.out
+++ b/point/test/expected/51_tpoint_tbl.test.out
@@ -624,46 +624,46 @@ SELECT MAX(getTimestamp(inst)) FROM tbl_tgeogpoint3Dinst;
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeompoint;
    max    
 ----------
- 04:16:00
+ 05:35:00
 (1 row)
 
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeogpoint;
    max    
 ----------
- 03:19:00
+ 04:47:00
 (1 row)
 
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeompoint3D;
    max    
 ----------
- 03:27:00
+ 04:34:00
 (1 row)
 
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeogpoint3D;
    max    
 ----------
- 03:53:00
+ 05:16:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeompoint;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeompoint;
    max    
 ----------
  05:35:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeogpoint;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeogpoint;
    max    
 ----------
  04:47:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeompoint3D;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeompoint3D;
    max    
 ----------
  04:34:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeogpoint3D;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeogpoint3D;
    max    
 ----------
  05:16:00
@@ -672,25 +672,25 @@ SELECT MAX(timespan(period(temp))) FROM tbl_tgeogpoint3D;
 SELECT MAX(timespan(temp)) FROM tbl_tgeompoint;
    max    
 ----------
- 04:16:00
+ 05:35:00
 (1 row)
 
 SELECT MAX(timespan(temp)) FROM tbl_tgeogpoint;
    max    
 ----------
- 03:19:00
+ 04:47:00
 (1 row)
 
 SELECT MAX(timespan(temp)) FROM tbl_tgeompoint3D;
    max    
 ----------
- 03:27:00
+ 04:34:00
 (1 row)
 
 SELECT MAX(timespan(temp)) FROM tbl_tgeogpoint3D;
    max    
 ----------
- 03:53:00
+ 05:16:00
 (1 row)
 
 SELECT MAX(numSequences(seq)) FROM tbl_tgeompointseq;
diff --git a/point/test/queries/50_stbox.test.sql b/point/test/queries/50_stbox.test.sql
index 5fe7e6c945..6402801c41 100644
--- a/point/test/queries/50_stbox.test.sql
+++ b/point/test/queries/50_stbox.test.sql
@@ -115,7 +115,7 @@ SELECT (geometry 'Polygon((1 1 1,1 2 2,2 2 2,2 1 1,1 1 1))'::box3d)::stbox;
 
 -------------------------------------------------------------------------------
 
-SELECT MAX(timespan(b::period)) FROM tbl_stbox;
+SELECT MAX(duration(b::period)) FROM tbl_stbox;
 SELECT MAX(ST_XMax(b::box2d)) FROM tbl_stbox;
 SELECT MAX(ST_XMax(b::box3d)) FROM tbl_stbox;
 
diff --git a/point/test/queries/51_tpoint.test.sql b/point/test/queries/51_tpoint.test.sql
index 194e4836e1..75e50ef4be 100644
--- a/point/test/queries/51_tpoint.test.sql
+++ b/point/test/queries/51_tpoint.test.sql
@@ -744,6 +744,15 @@ SELECT timespan(tgeogpoint '{Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-0
 SELECT timespan(tgeogpoint '[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03]');
 SELECT timespan(tgeogpoint '{[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03],[Point(3.5 3.5)@2000-01-04, Point(3.5 3.5)@2000-01-05]}');
 
+SELECT duration(tgeompoint 'Point(1 1)@2000-01-01');
+SELECT duration(tgeompoint '{Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03}');
+SELECT duration(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]');
+SELECT duration(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(3 3)@2000-01-04, Point(3 3)@2000-01-05]}');
+SELECT duration(tgeogpoint 'Point(1.5 1.5)@2000-01-01');
+SELECT duration(tgeogpoint '{Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03}');
+SELECT duration(tgeogpoint '[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03]');
+SELECT duration(tgeogpoint '{[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03],[Point(3.5 3.5)@2000-01-04, Point(3.5 3.5)@2000-01-05]}');
+
 SELECT numSequences(tgeompoint '[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03]');
 SELECT numSequences(tgeompoint '{[Point(1 1)@2000-01-01, Point(2 2)@2000-01-02, Point(1 1)@2000-01-03],[Point(3 3)@2000-01-04, Point(3 3)@2000-01-05]}');
 SELECT numSequences(tgeogpoint '[Point(1.5 1.5)@2000-01-01, Point(2.5 2.5)@2000-01-02, Point(1.5 1.5)@2000-01-03]');
diff --git a/point/test/queries/51_tpoint_tbl.test.sql b/point/test/queries/51_tpoint_tbl.test.sql
index 0912489084..9b3e77f1f6 100644
--- a/point/test/queries/51_tpoint_tbl.test.sql
+++ b/point/test/queries/51_tpoint_tbl.test.sql
@@ -186,10 +186,10 @@ SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeogpoint;
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeompoint3D;
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tgeogpoint3D;
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeompoint;
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeogpoint;
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeompoint3D;
-SELECT MAX(timespan(period(temp))) FROM tbl_tgeogpoint3D;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeompoint;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeogpoint;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeompoint3D;
+SELECT MAX(duration(period(temp))) FROM tbl_tgeogpoint3D;
 
 SELECT MAX(timespan(temp)) FROM tbl_tgeompoint;
 SELECT MAX(timespan(temp)) FROM tbl_tgeogpoint;
diff --git a/src/doublen.c b/src/doublen.c
index afef409dbb..94f4582dc9 100644
--- a/src/doublen.c
+++ b/src/doublen.c
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * doublen.c
- * Internal types used in particular for the average and centroid temporal
- * aggregates.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/geo_constructors.c b/src/geo_constructors.c
index 86da674af6..46893f106b 100644
--- a/src/geo_constructors.c
+++ b/src/geo_constructors.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * geo_constructors.c
- * Constructors for the 2D geometric operations
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/lifting.c b/src/lifting.c
index 2f7d0b7bc6..ec98c079d6 100644
--- a/src/lifting.c
+++ b/src/lifting.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * lifting.c
- * Generic functions for lifting functions and operators on temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -216,7 +213,7 @@ tfunc_tinstantset(const TInstantSet *ti, Datum param,
     TInstant *inst = tinstantset_inst_n(ti, i);
     instants[i] = tfunc_tinstant(inst, param, lfinfo);
   }
-  return tinstantset_make_free(instants, ti->count);
+  return tinstantset_make_free(instants, ti->count, MERGE_NO);
 }
 
 /**
@@ -358,7 +355,7 @@ tfunc_tinstantset_base(const TInstantSet *ti, Datum value, Oid valuetypid,
     TInstant *inst = tinstantset_inst_n(ti, i);
     instants[i] = tfunc_tinstant_base(inst, value, valuetypid, param, lfinfo);
   }
-  return tinstantset_make_free(instants, ti->count);
+  return tinstantset_make_free(instants, ti->count, MERGE_NO);
 }
 
 /**
@@ -840,7 +837,7 @@ sync_tfunc_tinstantset_tinstantset(const TInstantSet *ti1, const TInstantSet *ti
     else
       j++;
   }
-  return tinstantset_make_free(instants, k);
+  return tinstantset_make_free(instants, k, MERGE_NO);
 }
 
 /**
@@ -873,7 +870,7 @@ sync_tfunc_tsequence_tinstantset(const TSequence *seq, const TInstantSet *ti,
     if (seq->period.upper < inst->t)
       break;
   }
-  return tinstantset_make_free(instants, k);
+  return tinstantset_make_free(instants, k, MERGE_NO);
 }
 
 /**
@@ -930,7 +927,7 @@ sync_tfunc_tsequenceset_tinstantset(const TSequenceSet *ts, const TInstantSet *t
     else
       j++;
   }
-  return tinstantset_make_free(instants, k);
+  return tinstantset_make_free(instants, k, MERGE_NO);
 }
 
 /**
diff --git a/src/oidcache.c b/src/oidcache.c
index e990dabd51..35606809f8 100644
--- a/src/oidcache.c
+++ b/src/oidcache.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * oidcache.c
- * Functions for building a cache of Oids.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/period.c b/src/period.c
index cf00eec3e6..de0acb31be 100644
--- a/src/period.c
+++ b/src/period.c
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * period.c
- * Basic routines for period types composed of two timestamptz values and
- * two boolean values stating whether the bounds are inclusive or not
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,6 +24,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file period.c
+ * Basic routines for time periods composed of two `TimestampTz` values and
+ * two Boolean values stating whether the bounds are inclusive or not.
+ */
+
 #include "period.h"
 
 #include <assert.h>
@@ -626,21 +628,21 @@ period_shift_tscale(Period *result, const Interval *start,
 }
 
 /**
- * Returns the timespan of the period (internal function)
+ * Returns the duration of the period (internal function)
  */
 Interval *
-period_timespan_internal(const Period *p)
+period_duration_internal(const Period *p)
 {
   return DatumGetIntervalP(call_function2(timestamp_mi,
     TimestampTzGetDatum(p->upper), TimestampTzGetDatum(p->lower)));
 }
 
-PG_FUNCTION_INFO_V1(period_timespan);
+PG_FUNCTION_INFO_V1(period_duration);
 /**
- * Returns the timespan of the period
+ * Returns the duration of the period
  */
 PGDLLEXPORT Datum
-period_timespan(PG_FUNCTION_ARGS)
+period_duration(PG_FUNCTION_ARGS)
 {
   Period *p = PG_GETARG_PERIOD(0);
   Datum result = call_function2(timestamp_mi,
diff --git a/src/periodset.c b/src/periodset.c
index eb18b4ec06..9cc55f82e3 100644
--- a/src/periodset.c
+++ b/src/periodset.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * periodset.c
- * Basic functions for set of periods.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file periodset.c
+ * Basic functions for set of disjoint periods.
+ */
+
 #include "periodset.h"
 
 #include <assert.h>
@@ -492,6 +494,22 @@ PG_FUNCTION_INFO_V1(periodset_timespan);
  */
 PGDLLEXPORT Datum
 periodset_timespan(PG_FUNCTION_ARGS)
+{
+  PeriodSet *ps = PG_GETARG_PERIODSET(0);
+  Period *p1 = periodset_per_n(ps, 0);
+  Period *p2 = periodset_per_n(ps, ps->count - 1);
+  Datum result = call_function2(timestamp_mi, TimestampTzGetDatum(p2->upper),
+    TimestampTzGetDatum(p1->lower));
+  PG_FREE_IF_COPY(ps, 0);
+  PG_RETURN_DATUM(result);
+}
+
+PG_FUNCTION_INFO_V1(periodset_duration);
+/**
+ * Returns the timespan of the period set value
+ */
+PGDLLEXPORT Datum
+periodset_duration(PG_FUNCTION_ARGS)
 {
   PeriodSet *ps = PG_GETARG_PERIODSET(0);
   Period *p = periodset_per_n(ps, 0);
diff --git a/src/rangetypes_ext.c b/src/rangetypes_ext.c
index 5f10768e50..1d1a972efe 100644
--- a/src/rangetypes_ext.c
+++ b/src/rangetypes_ext.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * rangetypes_ext.c
- * Extension of operators for range types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,13 @@
  *
  *****************************************************************************/
 
+/**
+ * @file rangetypes_ext.c
+ * Extended operators for range types.
+ *
+ * These operators have been submitted as a PR to PostgreSQL.
+ */
+
 #include "rangetypes_ext.h"
 
 #include <assert.h>
diff --git a/src/sql/01_period.in.sql b/src/sql/01_period.in.sql
index aaa1debbf5..013f747541 100644
--- a/src/sql/01_period.in.sql
+++ b/src/sql/01_period.in.sql
@@ -120,9 +120,9 @@ CREATE FUNCTION upper_inc(period)
   AS 'MODULE_PATHNAME', 'period_upper_inc'
   LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
-CREATE FUNCTION timespan(period)
+CREATE FUNCTION duration(period)
   RETURNS interval
-  AS 'MODULE_PATHNAME', 'period_timespan'
+  AS 'MODULE_PATHNAME', 'period_duration'
   LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
 CREATE FUNCTION shift(period, interval)
diff --git a/src/sql/05_periodset.in.sql b/src/sql/05_periodset.in.sql
index 9a217bdca3..e78dfa7e2e 100644
--- a/src/sql/05_periodset.in.sql
+++ b/src/sql/05_periodset.in.sql
@@ -119,6 +119,11 @@ CREATE FUNCTION timespan(periodset)
   AS 'MODULE_PATHNAME', 'periodset_timespan'
   LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION duration(periodset)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'periodset_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION numPeriods(periodset)
   RETURNS integer
   AS 'MODULE_PATHNAME', 'periodset_num_periods'
diff --git a/src/sql/22_temporal.in.sql b/src/sql/22_temporal.in.sql
index 2b0863237d..42b121144a 100644
--- a/src/sql/22_temporal.in.sql
+++ b/src/sql/22_temporal.in.sql
@@ -732,6 +732,23 @@ CREATE FUNCTION timespan(ttext)
   AS 'MODULE_PATHNAME', 'temporal_timespan'
   LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION duration(tbool)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'temporal_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+CREATE FUNCTION duration(tint)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'temporal_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+CREATE FUNCTION duration(tfloat)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'temporal_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+CREATE FUNCTION duration(ttext)
+  RETURNS interval
+  AS 'MODULE_PATHNAME', 'temporal_duration'
+  LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION numSequences(tbool)
   RETURNS integer
   AS 'MODULE_PATHNAME', 'temporal_num_sequences'
diff --git a/src/tbool_boolops.c b/src/tbool_boolops.c
index 32c539a2ff..a01f519985 100644
--- a/src/tbool_boolops.c
+++ b/src/tbool_boolops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tbool_boolops.c
- * Temporal Boolean operators (and, or, not).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tbool_boolops.c
+ * Temporal Boolean operators (and, or, not).
+ */
+
 #include "tbool_boolops.h"
 
 #include "temporaltypes.h"
diff --git a/src/tbox.c b/src/tbox.c
index a195721d90..62bae32f1f 100644
--- a/src/tbox.c
+++ b/src/tbox.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tbox.c
- * Functions for temporal bounding boxes.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,6 +26,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tbox.c
+ * Functions for temporal bounding boxes.
+ */
+
 #include "tbox.h"
 
 #include <assert.h>
diff --git a/src/temporal.c b/src/temporal.c
index 647d9454a5..f22d43cd7e 100644
--- a/src/temporal.c
+++ b/src/temporal.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal.c
- * Basic functions for temporal types of any subtype.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal.c
+ * Basic functions for temporal types of any subtype.
+ */
+
 #include "temporal.h"
 
 #include <assert.h>
@@ -781,13 +783,14 @@ ensure_same_interpolation(const Temporal *temp1, const Temporal *temp2)
 
 /**
  * Ensures that the timestamp of the first temporal instant is smaller
- * than the one of the second temporal instant
+ * (or equal if the merge parameter is true) than the one of the second 
+ * temporal instant
  */
 void
 ensure_increasing_timestamps(const TInstant *inst1, const TInstant *inst2,
-  bool strict)
+  bool merge)
 {
-  if ((strict && inst1->t > inst2->t) || (!strict && inst1->t >= inst2->t))
+  if ((merge && inst1->t > inst2->t) || (!merge && inst1->t >= inst2->t))
   {
     char *t1 = call_output(TIMESTAMPTZOID, TimestampTzGetDatum(inst1->t));
     char *t2 = call_output(TIMESTAMPTZOID, TimestampTzGetDatum(inst2->t));
@@ -821,12 +824,12 @@ ensure_same_overlapping_value(const TInstant *inst1, const TInstant *inst2)
  * same dimensionality
  */
 void
-ensure_valid_tinstantarr(TInstant **instants, int count)
+ensure_valid_tinstantarr(TInstant **instants, int count, bool merge)
 {
   for (int i = 1; i < count; i++)
   {
     ensure_same_interpolation((Temporal *) instants[i - 1], (Temporal *) instants[i]);
-    ensure_increasing_timestamps(instants[i - 1], instants[i], false); /* >= */
+    ensure_increasing_timestamps(instants[i - 1], instants[i], merge);
     ensure_spatial_validity((Temporal *) instants[i - 1], (Temporal *) instants[i]);
   }
   return;
@@ -1135,7 +1138,7 @@ tinstantset_constructor(PG_FUNCTION_ARGS)
   int count;
   TInstant **instants = (TInstant **)temporalarr_extract(array, &count);
   ensure_tinstantarr(instants, count);
-  Temporal *result = (Temporal *)tinstantset_make(instants, count);
+  Temporal *result = (Temporal *)tinstantset_make(instants, count, MERGE_NO);
   pfree(instants);
   PG_FREE_IF_COPY(array, 0);
   PG_RETURN_POINTER(result);
@@ -2190,21 +2193,48 @@ temporal_timespan(PG_FUNCTION_ARGS)
   Temporal *temp = PG_GETARG_TEMPORAL(0);
   Datum result;
   ensure_valid_temptype(temp->temptype);
-  if (temp->temptype == INSTANT || temp->temptype == INSTANTSET)
+  if (temp->temptype == INSTANT)
   {
     Interval *interval = (Interval *) palloc(sizeof(Interval));
     interval->month = interval->day =  0;
     interval->time = (TimeOffset) 0;
     result = PointerGetDatum(interval);
   }
+  else if (temp->temptype == INSTANTSET)
+    result = tinstantset_timespan((TInstantSet *)temp);
   else if (temp->temptype == SEQUENCE)
-    result = tsequence_timespan((TSequence *)temp);
+    result = tsequence_duration((TSequence *)temp);
   else /* temp->temptype == SEQUENCESET */
     result = tsequenceset_timespan((TSequenceSet *)temp);
   PG_FREE_IF_COPY(temp, 0);
   PG_RETURN_DATUM(result);
 }
 
+PG_FUNCTION_INFO_V1(temporal_duration);
+/**
+ * Returns the duration of the temporal value
+ */
+PGDLLEXPORT Datum
+temporal_duration(PG_FUNCTION_ARGS)
+{
+  Temporal *temp = PG_GETARG_TEMPORAL(0);
+  Datum result;
+  ensure_valid_temptype(temp->temptype);
+  if (temp->temptype == INSTANT || temp->temptype == INSTANTSET)
+  {
+    Interval *interval = (Interval *) palloc(sizeof(Interval));
+    interval->month = interval->day = 0;
+    interval->time = (TimeOffset) 0;
+    result = PointerGetDatum(interval);
+  }
+  else if (temp->temptype == SEQUENCE)
+    result = tsequence_duration((TSequence *)temp);
+  else /* temp->temptype == SEQUENCESET */
+    result = tsequenceset_duration((TSequenceSet *)temp);
+  PG_FREE_IF_COPY(temp, 0);
+  PG_RETURN_DATUM(result);
+}
+
 PG_FUNCTION_INFO_V1(temporal_num_sequences);
 /**
  * Returns the number of sequences of the temporal sequence (set) value
diff --git a/src/temporal_aggfuncs.c b/src/temporal_aggfuncs.c
index 02f5668c1d..2e68b57a44 100644
--- a/src/temporal_aggfuncs.c
+++ b/src/temporal_aggfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_aggfuncs.c
- * Temporal aggregate functions
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_aggfuncs.c
+ * Temporal aggregate functions
+ */
+
 #include "temporal_aggfuncs.h"
 
 #include <assert.h>
@@ -1268,7 +1270,7 @@ temporal_tagg_finalfn(PG_FUNCTION_ARGS)
     values[0]->temptype == SEQUENCE);
   if (values[0]->temptype == INSTANT)
     result = (Temporal *)tinstantset_make((TInstant **)values,
-      state->length);
+      state->length, MERGE_NO);
   else /* values[0]->temptype == SEQUENCE */
     result = (Temporal *)tsequenceset_make((TSequence **)values,
       state->length, NORMALIZE);
@@ -1957,7 +1959,7 @@ tinstant_tavg_finalfn(TInstant **instants, int count)
     newinstants[i] = tinstant_make(Float8GetDatum(tavg), inst->t,
       FLOAT8OID);
   }
-  return tinstantset_make_free(newinstants, count);
+  return tinstantset_make_free(newinstants, count, MERGE_NO);
 }
 
 /**
diff --git a/src/temporal_analyze.c b/src/temporal_analyze.c
index c77bdc3475..18a16b694e 100644
--- a/src/temporal_analyze.c
+++ b/src/temporal_analyze.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_analyze.c
- * Functions for gathering statistics from temporal alphanumeric columns
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,7 +26,7 @@
 
 /**
  * @file temporal_analyze.c
- * Functions for gathering statistics from temporal alphanumber columns.
+ * Functions for gathering statistics from temporal alphanumeric columns.
  *
  * Various kind of statistics are collected for both the value and the time
  * dimension of temporal types. Please refer to the PostgreSQL file pg_statistic_d.h
diff --git a/src/temporal_boxops.c b/src/temporal_boxops.c
index f5c3950aab..ef3cb90080 100644
--- a/src/temporal_boxops.c
+++ b/src/temporal_boxops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_boxops.c
- * Bounding box operators for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -32,7 +29,7 @@
  * Bounding box operators for temporal types.
  *
  * The bounding box of temporal values are
- * - a `period` for temporal Booleans
+ * - a `Period` for temporal Booleans
  * - a `TBOX` for temporal integers and floats, where the *x* coordinate is for
  *   the value dimension and the *t* coordinate is for the time dimension.
  * The following operators are defined: `overlaps`, `contains`, `contained`, 
diff --git a/src/temporal_compops.c b/src/temporal_compops.c
index 87005601ae..e780e06237 100644
--- a/src/temporal_compops.c
+++ b/src/temporal_compops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_compops.c
- * Temporal comparison operators (=, <>, <, >, <=, >=).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_compops.c
+ * Temporal comparison operators (=, <>, <, >, <=, >=).
+ */
+
 #include "temporal_compops.h"
 
 #include <utils/lsyscache.h>
diff --git a/src/temporal_gist.c b/src/temporal_gist.c
index 1b4064b023..be96592017 100644
--- a/src/temporal_gist.c
+++ b/src/temporal_gist.c
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * temporal_gist.c
- * R-tree GiST index for temporal types where only the time dimension
- * is taken into account for indexing, currently, tbool and ttext.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,6 +24,12 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_gist.c
+ * R-tree GiST index for temporal types where only the time dimension
+ * is taken into account for indexing, currently, tbool and ttext.
+ */
+
 #include "temporal_gist.h"
 
 #include <access/gist.h>
diff --git a/src/temporal_parser.c b/src/temporal_parser.c
index 196c84c7bb..b1b7571105 100644
--- a/src/temporal_parser.c
+++ b/src/temporal_parser.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_parser.c
- * Functions for parsing time types and temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -498,7 +495,7 @@ tinstantset_parse(char **str, Oid basetype)
     instants[i] = tinstant_parse(str, basetype, false, true);
   }
   p_cbrace(str);
-  return tinstantset_make_free(instants, count);
+  return tinstantset_make_free(instants, count, MERGE_NO);
 }
 
 /**
diff --git a/src/temporal_posops.c b/src/temporal_posops.c
index 1de0abd4bc..ad5155b5f7 100644
--- a/src/temporal_posops.c
+++ b/src/temporal_posops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_posops.c
- * Relative position operators for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/temporal_selfuncs.c b/src/temporal_selfuncs.c
index 93e2ebb977..2294bd2e19 100644
--- a/src/temporal_selfuncs.c
+++ b/src/temporal_selfuncs.c
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * temporal_selfuncs.c
- * Functions for selectivity estimation of operators on temporal types whose
- * bounding box is a period, that is, tbool and ttext.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -31,7 +27,7 @@
 /**
  * @file temporal_selfuncs.c
  * Functions for selectivity estimation of operators on temporal types whose
- * bounding box is a period, that is, `tbool` and `ttext`.
+ * bounding box is a `Period`, that is, `tbool` and `ttext`.
  *
  * The operators currently supported are as follows
  * - B-tree comparison operators: `<`, `<=`, `>`, `>=`
diff --git a/src/temporal_spgist.c b/src/temporal_spgist.c
index f753b3ebd6..c86db299b4 100644
--- a/src/temporal_spgist.c
+++ b/src/temporal_spgist.c
@@ -1,12 +1,7 @@
 /*****************************************************************************
- *
- * temporal_spgist.c
- * Quad-tree SP-GiST index for temporal boolean and temporal text types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
- * These functions are based on those in the file rangetypes_spgist.c.
- *
  * Copyright (c) 2020, Université libre de Bruxelles and MobilityDB
  * contributors
  *
@@ -29,6 +24,13 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_spgist.c
+ * Quad-tree SP-GiST index for temporal boolean and temporal text types.
+ *
+ * These functions are based on those in the file `rangetypes_spgist.c`.
+ */
+
 #if MOBDB_PGSQL_VERSION >= 110000
 
 #include "temporal_spgist.h"
diff --git a/src/temporal_util.c b/src/temporal_util.c
index 4ce8d35e6f..84c9be5ac0 100644
--- a/src/temporal_util.c
+++ b/src/temporal_util.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_util.c
- * Miscellaneous utility functions for temporal types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_util.c
+ * Miscellaneous utility functions for temporal types.
+ */
+
 #include "temporal_util.h"
 
 #include <assert.h>
diff --git a/src/temporal_waggfuncs.c b/src/temporal_waggfuncs.c
index b172cc8327..fd959696ba 100644
--- a/src/temporal_waggfuncs.c
+++ b/src/temporal_waggfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * temporal_waggfuncs.c
- * Window temporal aggregate functions
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file temporal_waggfuncs.c
+ * Window temporal aggregate functions
+ */
+
 #include "temporal_waggfuncs.h"
 
 #include <utils/builtins.h>
diff --git a/src/time_analyze.c b/src/time_analyze.c
index c46e19ad4c..a92d0900b0 100644
--- a/src/time_analyze.c
+++ b/src/time_analyze.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_analyze.c
- * Functions for gathering statistics from time type columns
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/time_gist.c b/src/time_gist.c
index bef1939128..7355636c7f 100644
--- a/src/time_gist.c
+++ b/src/time_gist.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_gist.c
- * R-tree GiST index for time types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -31,7 +28,7 @@
  * @file time_gist.c
  * R-tree GiST index for time types.
  *
- * These functions are based on those in the file rangetypes_gist.c.
+ * These functions are based on those in the file `rangetypes_gist.c`.
  */
 
 #include "time_gist.h"
diff --git a/src/time_selfuncs.c b/src/time_selfuncs.c
index 945ca74604..f12e61cb6f 100644
--- a/src/time_selfuncs.c
+++ b/src/time_selfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_selfuncs.c
- * Functions for selectivity estimation of time types operators
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/time_spgist.c b/src/time_spgist.c
index 072d4fb20e..c65e74dd2b 100644
--- a/src/time_spgist.c
+++ b/src/time_spgist.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * time_spgist.c
- * Quad-tree SP-GiST index for time types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
diff --git a/src/timeops.c b/src/timeops.c
index 1d073ce2e8..94b13c4b28 100644
--- a/src/timeops.c
+++ b/src/timeops.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * timeops.c
- * Operators for time types.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file timeops.c
+ * Operators for time types.
+ */
+
 #include "timeops.h"
 
 #include <assert.h>
diff --git a/src/timestampset.c b/src/timestampset.c
index f6dac252bf..325918030c 100644
--- a/src/timestampset.c
+++ b/src/timestampset.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * timestampset.c
- * Basic functions for set of timestamps.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file timestampset.c
+ * Basic functions for set of (distinct) timestamps.
+ */
+
 #include "timestampset.h"
 
 #include <libpq/pqformat.h>
diff --git a/src/tinstant.c b/src/tinstant.c
index 2bf9743e93..5a06764912 100644
--- a/src/tinstant.c
+++ b/src/tinstant.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tinstant.c
- * Basic functions for temporal instants.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tinstant.c
+ * Basic functions for temporal instants.
+ */
+
 #include "tinstant.h"
 
 #include <assert.h>
@@ -188,7 +190,7 @@ tinstant_merge_array(TInstant **instants, int count)
     tinstantarr_sort(instants, count);
   int newcount = tinstantarr_remove_duplicates(instants, count);
   return (newcount == 1) ? (Temporal *) instants[0] :
-    (Temporal *) tinstantset_make(instants, newcount);
+    (Temporal *) tinstantset_make(instants, newcount, MERGE_NO);
 }
 
 /**
@@ -360,7 +362,7 @@ tfloatinst_to_tintinst(const TInstant *inst)
 TInstantSet *
 tinstant_to_tinstantset(const TInstant *inst)
 {
-  return tinstantset_make((TInstant **)&inst, 1);
+  return tinstantset_make((TInstant **)&inst, 1, MERGE_NO);
 }
 
 /**
diff --git a/src/tinstantset.c b/src/tinstantset.c
index 2e1c984790..7983d5472a 100644
--- a/src/tinstantset.c
+++ b/src/tinstantset.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tinstantset.c
- * Basic functions for temporal instant sets.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tinstantset.c
+ * Basic functions for temporal instant sets.
+ */
+
 #include "tinstantset.h"
 
 #include <assert.h>
@@ -89,11 +91,11 @@ tinstantset_bbox(void *box, const TInstantSet *ti)
  * Ensure the validity of the arguments when creating a temporal value
  */
 static void
-tinstantset_make_valid(TInstant **instants, int count)
+tinstantset_make_valid(TInstant **instants, int count, bool merge)
 {
   /* Test the validity of the instants */
   assert(count > 0);
-  ensure_valid_tinstantarr(instants, count);
+  ensure_valid_tinstantarr(instants, count, merge);
   return;
 }
 
@@ -171,11 +173,13 @@ tinstantset_make1(TInstant **instants, int count)
  *
  * @param[in] instants Array of instants
  * @param[in] count Number of elements in the array
+ * @param[in] merge True when overlapping instants are allowed as required in
+ * merge operations
  */
 TInstantSet *
-tinstantset_make(TInstant **instants, int count)
+tinstantset_make(TInstant **instants, int count, bool merge)
 {
-  tinstantset_make_valid(instants, count);
+  tinstantset_make_valid(instants, count, merge);
   return tinstantset_make1(instants, count);
 }
 
@@ -185,16 +189,18 @@ tinstantset_make(TInstant **instants, int count)
  *
  * @param[in] instants Array of instants
  * @param[in] count Number of elements in the array
+ * @param[in] merge True when overlapping instants are allowed as required in
+ * merge operations
  */
 TInstantSet *
-tinstantset_make_free(TInstant **instants, int count)
+tinstantset_make_free(TInstant **instants, int count, bool merge)
 {
   if (count == 0)
   {
     pfree(instants);
     return NULL;
   }
-  TInstantSet *result = tinstantset_make(instants, count);
+  TInstantSet *result = tinstantset_make(instants, count, merge);
   for (int i = 0; i < count; i++)
     pfree(instants[i]);
   pfree(instants);
@@ -210,7 +216,7 @@ tinstantset_from_base_internal(Datum value, Oid valuetypid, const TimestampSet *
   TInstant **instants = palloc(sizeof(TInstant *) * ts->count);
   for (int i = 0; i < ts->count; i++)
     instants[i] = tinstant_make(value, timestampset_time_n(ts, i), valuetypid);
-  return tinstantset_make_free(instants, ts->count);
+  return tinstantset_make_free(instants, ts->count, MERGE_NO);
 }
 
 PG_FUNCTION_INFO_V1(tinstantset_from_base);
@@ -236,7 +242,7 @@ tinstantset_append_tinstant(const TInstantSet *ti, const TInstant *inst)
   /* Ensure validity of the arguments */
   assert(ti->valuetypid == inst->valuetypid);
   TInstant *inst1 = tinstantset_inst_n(ti, ti->count - 1);
-  ensure_increasing_timestamps(inst1, inst, true); /* > */
+  ensure_increasing_timestamps(inst1, inst, MERGE);
   ensure_same_overlapping_value(inst1, inst);
   if (inst1->t == inst->t)
     return tinstantset_copy(ti);
@@ -311,7 +317,7 @@ tinstantset_merge_array(TInstantSet **instsets, int count)
   }
   /* Create the result */
   Temporal *result = (k == 1) ? (Temporal *) instants[0] :
-    (Temporal *) tinstantset_make(instants, totalcount);
+    (Temporal *) tinstantset_make(instants, totalcount, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -458,8 +464,8 @@ intersection_tinstantset_tinstantset(const TInstantSet *ti1, const TInstantSet *
   }
   if (k != 0)
   {
-    *inter1 = tinstantset_make(instants1, k);
-    *inter2 = tinstantset_make(instants2, k);
+    *inter1 = tinstantset_make(instants1, k, MERGE_NO);
+    *inter2 = tinstantset_make(instants2, k, MERGE_NO);
   }
 
   pfree(instants1); pfree(instants2);
@@ -528,7 +534,7 @@ tinstantset_read(StringInfo buf, Oid valuetypid)
   TInstant **instants = palloc(sizeof(TInstant *) * count);
   for (int i = 0; i < count; i++)
     instants[i] = tinstant_read(buf, valuetypid);
-  return tinstantset_make_free(instants, count);
+  return tinstantset_make_free(instants, count, MERGE_NO);
 }
 
 /*****************************************************************************
@@ -615,7 +621,7 @@ tsequenceset_to_tinstantset(const TSequenceSet *ts)
     TSequence *seq = tsequenceset_seq_n(ts, i);
     instants[i] = tsequence_inst_n(seq, 0);
   }
-  TInstantSet *result = tinstantset_make(instants, ts->count);
+  TInstantSet *result = tinstantset_make(instants, ts->count, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -767,6 +773,19 @@ tinstantset_period(Period *p, const TInstantSet *ti)
   return period_set(p, lower, upper, true, true);
 }
 
+/**
+ * Returns the timespan of the timestamp set value
+ */
+Datum
+tinstantset_timespan(const TInstantSet *ti)
+{
+  TimestampTz lower = tinstantset_start_timestamp(ti);
+  TimestampTz upper = tinstantset_end_timestamp(ti);
+  Datum result = call_function2(timestamp_mi, TimestampTzGetDatum(upper),
+    TimestampTzGetDatum(lower));
+  return result;
+}
+
 /**
  * Returns the instants of the temporal value as a C array
  */
@@ -1038,7 +1057,7 @@ tinstantset_restrict_value(const TInstantSet *ti, Datum value, bool atfunc)
       instants[count++] = inst;
   }
   TInstantSet *result = (count == 0) ? NULL :
-    tinstantset_make(instants, count);
+    tinstantset_make(instants, count, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -1077,7 +1096,7 @@ tinstantset_restrict_values(const TInstantSet *ti, const Datum *values,
       instants[newcount++] = inst;
   }
   TInstantSet *result = (newcount == 0) ? NULL :
-    tinstantset_make(instants, newcount);
+    tinstantset_make(instants, newcount, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -1108,7 +1127,7 @@ tnumberinstset_restrict_range(const TInstantSet *ti, RangeType *range, bool atfu
       instants[count++] = inst;
   }
   TInstantSet *result = (count == 0) ? NULL :
-    tinstantset_make(instants, count);
+    tinstantset_make(instants, count, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -1149,7 +1168,7 @@ tnumberinstset_restrict_ranges(const TInstantSet *ti, RangeType **normranges,
       instants[newcount++] = inst;
   }
   TInstantSet *result = (newcount == 0) ? NULL :
-    tinstantset_make(instants, newcount);
+    tinstantset_make(instants, newcount, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -1249,7 +1268,7 @@ tinstantset_restrict_timestamp(const TInstantSet *ti, TimestampTz t, bool atfunc
         instants[count++] = inst;
     }
     TInstantSet *result = (count == 0) ? NULL :
-      tinstantset_make(instants, count);
+      tinstantset_make(instants, count, MERGE_NO);
     pfree(instants);
     return (Temporal *)result;
   }
@@ -1273,7 +1292,7 @@ tinstantset_restrict_timestampset(const TInstantSet *ti,
     if (temp == NULL || temp->temptype == INSTANTSET)
       return (TInstantSet *) temp;
     inst = (TInstant *) temp;
-    result = tinstantset_make(&inst, 1);
+    result = tinstantset_make(&inst, 1, MERGE_NO);
     pfree(inst);
     return result;
   }
@@ -1324,7 +1343,7 @@ tinstantset_restrict_timestampset(const TInstantSet *ti,
     while (i < ti->count)
       instants[k++] = tinstantset_inst_n(ti, i++);
   }
-  result = (k == 0) ? NULL : tinstantset_make(instants, k);
+  result = (k == 0) ? NULL : tinstantset_make(instants, k, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -1357,7 +1376,7 @@ tinstantset_restrict_period(const TInstantSet *ti, const Period *period,
       instants[count++] = inst;
   }
   TInstantSet *result = (count == 0) ? NULL :
-    tinstantset_make(instants, count);
+    tinstantset_make(instants, count, MERGE_NO);
   pfree(instants);
   return result;
 }
@@ -1402,7 +1421,7 @@ tinstantset_restrict_periodset(const TInstantSet *ti, const PeriodSet *ps,
       instants[count++] = inst;
   }
   TInstantSet *result = (count == 0) ? NULL :
-    tinstantset_make(instants, count);
+    tinstantset_make(instants, count, MERGE_NO);
   pfree(instants);
   return result;
 }
diff --git a/src/tnumber_distance.c b/src/tnumber_distance.c
index e080231f9f..45a79b73d1 100644
--- a/src/tnumber_distance.c
+++ b/src/tnumber_distance.c
@@ -1,7 +1,4 @@
 /***********************************************************************
- *
- * tnumber_distance.c
- * Distance functions for temporal numbers.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_distance.c
+ * Distance functions for temporal numbers.
+ */
+
 #include "tnumber_distance.h"
 
 #include <assert.h>
@@ -77,6 +79,7 @@ datum_distance(Datum l, Datum r, Oid typel, Oid typer)
  * @param[in] seq Temporal number
  * @param[in] value Value
  * @param[in] valuetypid Type of the base value
+ * @param[in] restypid Type of the result
  */
 static TSequence *
 distance_tnumberseq_base(const TSequence *seq, Datum value, Oid valuetypid,
@@ -123,7 +126,7 @@ distance_tnumberseq_base(const TSequence *seq, Datum value, Oid valuetypid,
  * @param[in] ts Temporal number
  * @param[in] value Value
  * @param[in] valuetypid Type of the base value
-
+ * @param[in] restypid Type of the result
  */
 static TSequenceSet *
 distance_tnumberseqset_base(const TSequenceSet *ts, Datum value, Oid valuetypid,
@@ -143,6 +146,11 @@ distance_tnumberseqset_base(const TSequenceSet *ts, Datum value, Oid valuetypid,
 /**
  * Returns the temporal distance between the temporal number and the
  * value (distpatch function)
+ *
+ * @param[in] temp Temporal number
+ * @param[in] value Value
+ * @param[in] valuetypid Type of the base value
+ * @param[in] restypid Type of the result
  */
 static Temporal *
 distance_tnumber_base_internal(const Temporal *temp, Datum value,
@@ -216,6 +224,9 @@ distance_tnumber_base(PG_FUNCTION_ARGS)
 /**
  * Returns the temporal distance between the two temporal points
  * (dispatch function)
+ *
+ * @param[in] temp1,temp2 Temporal numbers
+ * @param[in] restypid Type of the result
  */
 static Temporal *
 distance_tnumber_tnumber_internal(const Temporal *temp1, const Temporal *temp2,
diff --git a/src/tnumber_gist.c b/src/tnumber_gist.c
index 1ff5933203..9057f44d2f 100644
--- a/src/tnumber_gist.c
+++ b/src/tnumber_gist.c
@@ -1,9 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_gist.c
- * R-tree GiST index for temporal integers and temporal floats
- *
- * These functions are based on those in the file gistproc.c.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -29,6 +24,13 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_gist.c
+ * R-tree GiST index for temporal integers and temporal floats
+ *
+ * These functions are based on those in the file `gistproc.c`.
+ */
+
 #include "tnumber_gist.h"
 
 #include <assert.h>
diff --git a/src/tnumber_mathfuncs.c b/src/tnumber_mathfuncs.c
index 1db5e6de2a..1358c0f9e3 100644
--- a/src/tnumber_mathfuncs.c
+++ b/src/tnumber_mathfuncs.c
@@ -1,8 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_mathfuncs.c
- * Temporal mathematical operators (+, -, *, /) and functions (round,
- * degrees).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -28,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_mathfuncs.c
+ * Temporal mathematical operators (+, -, *, /) and functions (round, degrees).
+ */
+
 #include "tnumber_mathfuncs.h"
 
 #include <assert.h>
diff --git a/src/tnumber_selfuncs.c b/src/tnumber_selfuncs.c
index 8c63b5d035..a05f08a35d 100644
--- a/src/tnumber_selfuncs.c
+++ b/src/tnumber_selfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tnumber_selfuncs.c
- * Functions for selectivity estimation of operators on temporal number types
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tnumber_selfuncs.c
+ * Functions for selectivity estimation of operators on temporal number types
+ */
+
 #include "tnumber_selfuncs.h"
 
 #include <assert.h>
diff --git a/src/tnumber_spgist.c b/src/tnumber_spgist.c
index add598985a..31718e322d 100644
--- a/src/tnumber_spgist.c
+++ b/src/tnumber_spgist.c
@@ -1,9 +1,5 @@
 /*****************************************************************************
  *
- * tnumber_spgist.c
- * SP-GiST implementation of 4-dimensional quad tree over temporal integers
- * and floats.
- * 
  * This MobilityDB code is provided under The PostgreSQL License.
  *
  * Copyright (c) 2020, Université libre de Bruxelles and MobilityDB
@@ -30,10 +26,10 @@
 
 /**
  * @file tnumber_spgist.c
- * SP-GiST implementation of 4-dimensional quad tree over temporal integers
- * and floats.
+ * SP-GiST implementation of 4-dimensional quad-tree over temporal integers
+ * and temporal floats.
  *
- * These functions are based on those in the file geo_spgist.c. from
+ * These functions are based on those in the file ``geo_spgist.c`. from
  * PostgreSQL. This module provides SP-GiST implementation for temporal
  * number types using a quad tree analogy in 4-dimensional space. Notice
  * that SP-GiST doesn't allow indexing of overlapping objects.  We are
diff --git a/src/tsequence.c b/src/tsequence.c
index 7af6be2d8a..f46b807326 100644
--- a/src/tsequence.c
+++ b/src/tsequence.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tsequence.c
- * Basic functions for temporal sequences.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tsequence.c
+ * Basic functions for temporal sequences.
+ */
+
 #include "tsequence.h"
 
 #include <assert.h>
@@ -720,120 +722,6 @@ tinstantarr_normalize(TInstant **instants, bool linear, int count,
   return result;
 }
 
-/**
- * Normalize the array of temporal sequence values
- *
- * The inpuy sequences may be non-contiguous but must ordered and
- * either (1) are non-overlapping, or (2) share the same last/first
- * instant in the case we are merging temporal sequences.
- *
- * @param[in] sequences Array of input sequences
- * @param[in] count Number of elements in the input array
- * @param[out] newcount Number of elements in the output array
- * @result Array of normalized temporal sequences values
- * @pre Each sequence in the input array is normalized
- * @pre When merging sequences, the test whether the value is the same
- * at the common instant should be ensured by the calling function.
- * @note The function creates new sequences and does not free the original
- * sequences
- */
-TSequence **
-tsequencearr_normalize(TSequence **sequences, int count, int *newcount)
-{
-  TSequence **result = palloc(sizeof(TSequence *) * count);
-  /* seq1 is the sequence to which we try to join subsequent seq2 */
-  TSequence *seq1 = sequences[0];
-  Oid valuetypid = seq1->valuetypid;
-  bool linear = MOBDB_FLAGS_GET_LINEAR(seq1->flags);
-  bool isnew = false;
-  int k = 0;
-  for (int i = 1; i < count; i++)
-  {
-    TSequence *seq2 = sequences[i];
-    TInstant *last2 = (seq1->count == 1) ? NULL :
-      tsequence_inst_n(seq1, seq1->count - 2);
-    Datum last2value = (seq1->count == 1) ? 0 :
-      tinstant_value(last2);
-    TInstant *last1 = tsequence_inst_n(seq1, seq1->count - 1);
-    Datum last1value = tinstant_value(last1);
-    TInstant *first1 = tsequence_inst_n(seq2, 0);
-    Datum first1value = tinstant_value(first1);
-    TInstant *first2 = (seq2->count == 1) ? NULL :
-      tsequence_inst_n(seq2, 1);
-    Datum first2value = (seq2->count == 1) ? 0 :
-      tinstant_value(first2);
-    bool adjacent = seq1->period.upper == seq2->period.lower &&
-      (seq1->period.upper_inc || seq2->period.lower_inc);
-    /* If they are adjacent and not instantaneous */
-    if (adjacent && last2 != NULL && first2 != NULL &&
-      (
-      /* If step and the last segment of the first sequence is constant
-         ..., 1@t1, 1@t2) [1@t2, 1@t3, ... -> ..., 1@t1, 2@t3, ...
-         ..., 1@t1, 1@t2) [1@t2, 2@t3, ... -> ..., 1@t1, 2@t3, ...
-         ..., 1@t1, 1@t2] (1@t2, 2@t3, ... -> ..., 1@t1, 2@t3, ...
-       */
-      (!linear &&
-      datum_eq(last2value, last1value, valuetypid) &&
-      datum_eq(last1value, first1value, valuetypid))
-      ||
-      /* If the last/first segments are constant and equal
-         ..., 1@t1, 1@t2] (1@t2, 1@t3, ... -> ..., 1@t1, 1@t3, ...
-       */
-      (datum_eq(last2value, last1value, valuetypid) &&
-      datum_eq(last1value, first1value, valuetypid) &&
-      datum_eq(first1value, first2value, valuetypid))
-      ||
-      /* If float/point sequences and collinear last/first segments having the same duration
-         ..., 1@t1, 2@t2) [2@t2, 3@t3, ... -> ..., 1@t1, 3@t3, ...
-      */
-      (datum_eq(last1value, first1value, valuetypid) &&
-      datum_collinear(valuetypid, last2value, first1value, first2value,
-        last2->t, first1->t, first2->t))
-      ))
-    {
-      /* Remove the last and first instants of the sequences */
-      seq1 = tsequence_join(seq1, seq2, true, true);
-      isnew = true;
-    }
-    /* If step sequences and the first one has an exclusive upper bound,
-       by definition the first sequence has the last segment constant
-       ..., 1@t1, 1@t2) [2@t2, 3@t3, ... -> ..., 1@t1, 2@t2, 3@t3, ...
-       ..., 1@t1, 1@t2) [2@t2] -> ..., 1@t1, 2@t2]
-     */
-    else if (adjacent && !linear && !seq1->period.upper_inc)
-    {
-      /* Remove the last instant of the first sequence */
-      seq1 = tsequence_join(seq1, seq2, true, false);
-      isnew = true;
-    }
-    /* If they are adjacent and have equal last/first value respectively
-      Stewise
-      ... 1@t1, 2@t2], (2@t2, 1@t3, ... -> ..., 1@t1, 2@t2, 1@t3, ...
-      [1@t1], (1@t1, 2@t2, ... -> ..., 1@t1, 2@t2
-      Linear
-      ..., 1@t1, 2@t2), [2@t2, 1@t3, ... -> ..., 1@t1, 2@t2, 1@t3, ...
-      ..., 1@t1, 2@t2], (2@t2, 1@t3, ... -> ..., 1@t1, 2@t2, 1@t3, ...
-      ..., 1@t1, 2@t2), [2@t2] -> ..., 1@t1, 2@t2]
-      [1@t1],(1@t1, 2@t2, ... -> [1@t1, 2@t2, ...
-    */
-    else if (adjacent && datum_eq(last1value, first1value, valuetypid))
-    {
-      /* Remove the first instant of the second sequence */
-      seq1 = tsequence_join(seq1, seq2, false, true);
-      isnew = true;
-    }
-    else
-    {
-      result[k++] = isnew ? seq1 : tsequence_copy(seq1);
-      seq1 = seq2;
-      isnew = false;
-    }
-  }
-  result[k++] = isnew ? seq1 : tsequence_copy(seq1);
-  *newcount = k;
-  return result;
-}
-
 /*****************************************************************************/
 
 /**
@@ -904,7 +792,7 @@ tsequence_make_valid(TInstant **instants, int count, bool lower_inc, bool upper_
       tinstant_value(instants[count - 2]), instants[0]->valuetypid))
     ereport(ERROR, (errcode(ERRCODE_RESTRICT_VIOLATION),
       errmsg("Invalid end value for temporal sequence")));
-  ensure_valid_tinstantarr(instants, count);
+  ensure_valid_tinstantarr(instants, count, MERGE_NO);
   return;
 }
 
@@ -1063,38 +951,6 @@ tsequence_make_free(TInstant **instants, int count, bool lower_inc,
   return result;
 }
 
-/**
- * Join the two temporal sequence values
- *
- * @param[in] seq1,seq2 Temporal sequence values
- * @param[in] removelast,removefirst Remove the last and/or the
- * first instant of the first/second sequence
- * @pre The two input sequences are adjacent and have the same interpolation
- * @note The function is called when normalizing an array of sequences
- * and thus, all validity tests have been already made
- */
-TSequence *
-tsequence_join(const TSequence *seq1, const TSequence *seq2,
-  bool removelast, bool removefirst)
-{
-  ensure_same_interpolation((Temporal *) seq1, (Temporal *) seq2);
-
-  int count1 = removelast ? seq1->count - 1 : seq1->count;
-  int start2 = removefirst ? 1 : 0;
-  int count = count1 + (seq2->count - start2);
-  TInstant **instants = palloc(sizeof(TSequence *) * count);
-  int k = 0;
-  for (int i = 0; i < count1; i++)
-    instants[k++] = tsequence_inst_n(seq1, i);
-  for (int i = start2; i < seq2->count; i++)
-    instants[k++] = tsequence_inst_n(seq2, i);
-  TSequence *result = tsequence_make1(instants, count,
-    seq1->period.lower_inc, seq2->period.upper_inc,
-    MOBDB_FLAGS_GET_LINEAR(seq1->flags), NORMALIZE_NO);
-  pfree(instants);
-  return result;
-}
-
 /**
  * Construct a temporal sequence value from a base value and a period
  * (internal function)
@@ -1133,6 +989,150 @@ tsequence_from_base(PG_FUNCTION_ARGS)
   PG_RETURN_POINTER(result);
 }
 
+/**
+ * Join the two temporal sequence values
+ *
+ * @param[in] seq1,seq2 Temporal sequence values
+ * @param[in] removelast,removefirst Remove the last and/or the
+ * first instant of the first/second sequence
+ * @pre The two input sequences are adjacent and have the same interpolation
+ * @note The function is called when normalizing an array of sequences
+ * and thus, all validity tests have been already made
+ */
+static TSequence *
+tsequence_join(const TSequence *seq1, const TSequence *seq2,
+  bool removelast, bool removefirst)
+{
+  int count1 = removelast ? seq1->count - 1 : seq1->count;
+  int start2 = removefirst ? 1 : 0;
+  int count = count1 + (seq2->count - start2);
+  TInstant **instants = palloc(sizeof(TSequence *) * count);
+  int k = 0;
+  for (int i = 0; i < count1; i++)
+    instants[k++] = tsequence_inst_n(seq1, i);
+  for (int i = start2; i < seq2->count; i++)
+    instants[k++] = tsequence_inst_n(seq2, i);
+  TSequence *result = tsequence_make1(instants, count,
+    seq1->period.lower_inc, seq2->period.upper_inc,
+    MOBDB_FLAGS_GET_LINEAR(seq1->flags), NORMALIZE_NO);
+  pfree(instants);
+  return result;
+}
+
+/**
+ * Normalize the array of temporal sequence values
+ *
+ * The inpuy sequences may be non-contiguous but must ordered and
+ * either (1) are non-overlapping, or (2) share the same last/first
+ * instant in the case we are merging temporal sequences.
+ *
+ * @param[in] sequences Array of input sequences
+ * @param[in] count Number of elements in the input array
+ * @param[out] newcount Number of elements in the output array
+ * @result Array of normalized temporal sequences values
+ * @pre Each sequence in the input array is normalized
+ * @pre When merging sequences, the test whether the value is the same
+ * at the common instant should be ensured by the calling function.
+ * @note The function creates new sequences and does not free the original
+ * sequences
+ */
+TSequence **
+tsequencearr_normalize(TSequence **sequences, int count, int *newcount)
+{
+  TSequence **result = palloc(sizeof(TSequence *) * count);
+  /* seq1 is the sequence to which we try to join subsequent seq2 */
+  TSequence *seq1 = sequences[0];
+  Oid valuetypid = seq1->valuetypid;
+  bool linear = MOBDB_FLAGS_GET_LINEAR(seq1->flags);
+  bool isnew = false;
+  int k = 0;
+  for (int i = 1; i < count; i++)
+  {
+    TSequence *seq2 = sequences[i];
+    TInstant *last2 = (seq1->count == 1) ? NULL :
+      tsequence_inst_n(seq1, seq1->count - 2);
+    Datum last2value = (seq1->count == 1) ? 0 :
+      tinstant_value(last2);
+    TInstant *last1 = tsequence_inst_n(seq1, seq1->count - 1);
+    Datum last1value = tinstant_value(last1);
+    TInstant *first1 = tsequence_inst_n(seq2, 0);
+    Datum first1value = tinstant_value(first1);
+    TInstant *first2 = (seq2->count == 1) ? NULL :
+      tsequence_inst_n(seq2, 1);
+    Datum first2value = (seq2->count == 1) ? 0 :
+      tinstant_value(first2);
+    bool adjacent = seq1->period.upper == seq2->period.lower &&
+      (seq1->period.upper_inc || seq2->period.lower_inc);
+    /* If they are adjacent and not instantaneous */
+    if (adjacent && last2 != NULL && first2 != NULL &&
+      (
+      /* If step and the last segment of the first sequence is constant
+         ..., 1@t1, 1@t2) [1@t2, 1@t3, ... -> ..., 1@t1, 2@t3, ...
+         ..., 1@t1, 1@t2) [1@t2, 2@t3, ... -> ..., 1@t1, 2@t3, ...
+         ..., 1@t1, 1@t2] (1@t2, 2@t3, ... -> ..., 1@t1, 2@t3, ...
+       */
+      (!linear &&
+      datum_eq(last2value, last1value, valuetypid) &&
+      datum_eq(last1value, first1value, valuetypid))
+      ||
+      /* If the last/first segments are constant and equal
+         ..., 1@t1, 1@t2] (1@t2, 1@t3, ... -> ..., 1@t1, 1@t3, ...
+       */
+      (datum_eq(last2value, last1value, valuetypid) &&
+      datum_eq(last1value, first1value, valuetypid) &&
+      datum_eq(first1value, first2value, valuetypid))
+      ||
+      /* If float/point sequences and collinear last/first segments having the same duration
+         ..., 1@t1, 2@t2) [2@t2, 3@t3, ... -> ..., 1@t1, 3@t3, ...
+      */
+      (datum_eq(last1value, first1value, valuetypid) &&
+      datum_collinear(valuetypid, last2value, first1value, first2value,
+        last2->t, first1->t, first2->t))
+      ))
+    {
+      /* Remove the last and first instants of the sequences */
+      seq1 = tsequence_join(seq1, seq2, true, true);
+      isnew = true;
+    }
+    /* If step sequences and the first one has an exclusive upper bound,
+       by definition the first sequence has the last segment constant
+       ..., 1@t1, 1@t2) [2@t2, 3@t3, ... -> ..., 1@t1, 2@t2, 3@t3, ...
+       ..., 1@t1, 1@t2) [2@t2] -> ..., 1@t1, 2@t2]
+     */
+    else if (adjacent && !linear && !seq1->period.upper_inc)
+    {
+      /* Remove the last instant of the first sequence */
+      seq1 = tsequence_join(seq1, seq2, true, false);
+      isnew = true;
+    }
+    /* If they are adjacent and have equal last/first value respectively
+      Stewise
+      ... 1@t1, 2@t2], (2@t2, 1@t3, ... -> ..., 1@t1, 2@t2, 1@t3, ...
+      [1@t1], (1@t1, 2@t2, ... -> ..., 1@t1, 2@t2
+      Linear
+      ..., 1@t1, 2@t2), [2@t2, 1@t3, ... -> ..., 1@t1, 2@t2, 1@t3, ...
+      ..., 1@t1, 2@t2], (2@t2, 1@t3, ... -> ..., 1@t1, 2@t2, 1@t3, ...
+      ..., 1@t1, 2@t2), [2@t2] -> ..., 1@t1, 2@t2]
+      [1@t1],(1@t1, 2@t2, ... -> [1@t1, 2@t2, ...
+    */
+    else if (adjacent && datum_eq(last1value, first1value, valuetypid))
+    {
+      /* Remove the first instant of the second sequence */
+      seq1 = tsequence_join(seq1, seq2, false, true);
+      isnew = true;
+    }
+    else
+    {
+      result[k++] = isnew ? seq1 : tsequence_copy(seq1);
+      seq1 = seq2;
+      isnew = false;
+    }
+  }
+  result[k++] = isnew ? seq1 : tsequence_copy(seq1);
+  *newcount = k;
+  return result;
+}
+
 /**
  * Append an instant to the temporal value
  */
@@ -1143,7 +1143,7 @@ tsequence_append_tinstant(const TSequence *seq, const TInstant *inst)
   assert(seq->valuetypid == inst->valuetypid);
   bool linear = MOBDB_FLAGS_GET_LINEAR(seq->flags);
   TInstant *inst1 = tsequence_inst_n(seq, seq->count - 1);
-  ensure_increasing_timestamps(inst1, inst, true); /* > */
+  ensure_increasing_timestamps(inst1, inst, MERGE);
   if (inst1->t == inst->t)
   {
     bool seqresult = datum_eq(tinstant_value(inst1), tinstant_value(inst), inst1->valuetypid);
@@ -1151,7 +1151,7 @@ tsequence_append_tinstant(const TSequence *seq, const TInstant *inst)
     {
       char *t1 = call_output(TIMESTAMPTZOID, TimestampTzGetDatum(inst1->t));
       ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR),
-        errmsg("The temporal values have different value at their overlapping instant %s", t1)));
+        errmsg("The temporal values have different value at their common instant %s", t1)));
     }
     /* The result is a sequence set */
     if (linear && ! seqresult)
@@ -1248,13 +1248,13 @@ tsequence_merge_array1(TSequence **sequences, int count, int *totalcount)
       ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR),
         errmsg("The temporal values cannot overlap on time: %s, %s", t1, t2)));
     }
-    if (inst1->t == inst2->t && seq1->period.upper_inc && seq2->period.lower_inc)
+    else if (inst1->t == inst2->t && seq1->period.upper_inc && seq2->period.lower_inc)
     {
       if (! datum_eq(tinstant_value(inst1), tinstant_value(inst2), inst1->valuetypid))
       {
         t1 = call_output(TIMESTAMPTZOID, TimestampTzGetDatum(inst1->t));
         ereport(ERROR, (errcode(ERRCODE_INTERNAL_ERROR),
-          errmsg("The temporal values have different value at their overlapping instant %s", t1)));
+          errmsg("The temporal values have different value at their common instant %s", t1)));
       }
     }
     seq1 = seq2;
@@ -1443,8 +1443,8 @@ intersection_tsequence_tinstantset(const TSequence *seq, const TInstantSet *ti,
     return false;
   }
 
-  *inter1 = tinstantset_make_free(instants1, k);
-  *inter2 = tinstantset_make(instants2, k);
+  *inter1 = tinstantset_make_free(instants1, k, MERGE_NO);
+  *inter2 = tinstantset_make(instants2, k, MERGE_NO);
   pfree(instants2);
   return true;
 }
@@ -2096,12 +2096,12 @@ tsequence_max_value(const TSequence *seq)
 }
 
 /**
- * Returns the timespan of the temporal value
+ * Returns the duration of the temporal value
  */
 Datum
-tsequence_timespan(const TSequence *seq)
+tsequence_duration(const TSequence *seq)
 {
-  Interval *result = period_timespan_internal(&seq->period);
+  Interval *result = period_duration_internal(&seq->period);
   return PointerGetDatum(result);
 }
 
@@ -3587,7 +3587,7 @@ tsequence_at_timestampset(const TSequence *seq, const TimestampSet *ts)
     inst = tsequence_at_timestamp(seq, timestampset_time_n(ts, 0));
     if (inst == NULL)
       return (TInstantSet *) NULL;
-    return tinstantset_make(&inst, 1);
+    return tinstantset_make(&inst, 1, MERGE_NO);
   }
 
   /* Bounding box test */
@@ -3602,7 +3602,7 @@ tsequence_at_timestampset(const TSequence *seq, const TimestampSet *ts)
   {
     if (!contains_timestampset_timestamp_internal(ts, inst->t))
       return NULL;
-    return tinstantset_make(&inst, 1);
+    return tinstantset_make(&inst, 1, MERGE_NO);
   }
 
   /* General case */
@@ -3618,7 +3618,7 @@ tsequence_at_timestampset(const TSequence *seq, const TimestampSet *ts)
     if (inst != NULL)
       instants[k++] = inst;
   }
-  return tinstantset_make_free(instants, k);
+  return tinstantset_make_free(instants, k, MERGE_NO);
 }
 
 /*****************************************************************************/
diff --git a/src/tsequenceset.c b/src/tsequenceset.c
index c723219900..383a24729f 100644
--- a/src/tsequenceset.c
+++ b/src/tsequenceset.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * tsequenceset.c
- * Basic functions for temporal sequence sets.
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file tsequenceset.c
+ * Basic functions for temporal sequence sets.
+ */
+
 #include "tsequenceset.h"
 
 #include <assert.h>
@@ -460,8 +462,8 @@ intersection_tsequenceset_tinstantset(const TSequenceSet *ts, const TInstantSet
     return false;
   }
 
-  *inter1 = tinstantset_make_free(instants1, k);
-  *inter2 = tinstantset_make(instants2, k);
+  *inter1 = tinstantset_make_free(instants1, k, MERGE_NO);
+  *inter2 = tinstantset_make(instants2, k, MERGE_NO);
   pfree(instants2);
   return true;
 }
@@ -981,6 +983,19 @@ tsequenceset_get_time(const TSequenceSet *ts)
  */
 Datum
 tsequenceset_timespan(const TSequenceSet *ts)
+{
+  TSequence *seq1 = tsequenceset_seq_n(ts, 0);
+  TSequence *seq2 = tsequenceset_seq_n(ts, ts->count - 1);
+  Datum result = call_function2(timestamp_mi,
+    TimestampTzGetDatum(seq2->period.upper), TimestampTzGetDatum(seq1->period.lower));
+  return result;
+}
+
+/**
+ * Returns the duration of the temporal value
+ */
+Datum
+tsequenceset_duration(const TSequenceSet *ts)
 {
   TSequence *seq = tsequenceset_seq_n(ts, 0);
   Datum result = call_function2(timestamp_mi,
@@ -1730,7 +1745,7 @@ tsequenceset_restrict_timestampset(const TSequenceSet *ts1,
     if (atfunc && temp != NULL)
     {
       TInstant *inst = (TInstant *) temp;
-      Temporal *result = (Temporal *) tinstantset_make(&inst, 1);
+      Temporal *result = (Temporal *) tinstantset_make(&inst, 1, MERGE_NO);
       pfree(inst);
       return result;
     }
@@ -1774,7 +1789,7 @@ tsequenceset_restrict_timestampset(const TSequenceSet *ts1,
           j++;
       }
     }
-    return (Temporal *) tinstantset_make_free(instants, count);
+    return (Temporal *) tinstantset_make_free(instants, count, MERGE_NO);
   }
   else
   {
diff --git a/src/ttext_textfuncs.c b/src/ttext_textfuncs.c
index 4607539d5c..685ca407e7 100644
--- a/src/ttext_textfuncs.c
+++ b/src/ttext_textfuncs.c
@@ -1,7 +1,4 @@
 /*****************************************************************************
- *
- * ttext_textfuncs.c
- * Temporal text functions (textcat, lower, upper).
  *
  * This MobilityDB code is provided under The PostgreSQL License.
  *
@@ -27,6 +24,11 @@
  *
  *****************************************************************************/
 
+/**
+ * @file ttext_textfuncs.c
+ * Temporal text functions: `textcat`, `lower`, `upper`.
+ */
+
 #include "ttext_textfuncs.h"
 
 #include <utils/builtins.h>
diff --git a/test/expected/01_period.test.out b/test/expected/01_period.test.out
index 7d9f751620..6706b8df7f 100644
--- a/test/expected/01_period.test.out
+++ b/test/expected/01_period.test.out
@@ -223,32 +223,32 @@ SELECT upper_inc(period '(2000-01-01,2000-01-02)');
  f
 (1 row)
 
-SELECT timespan(period '[2000-01-01,2000-01-01]');
- timespan 
+SELECT duration(period '[2000-01-01,2000-01-01]');
+ duration 
 ----------
  00:00:00
 (1 row)
 
-SELECT timespan(period '[2000-01-01,2000-01-02]');
- timespan 
+SELECT duration(period '[2000-01-01,2000-01-02]');
+ duration 
 ----------
  1 day
 (1 row)
 
-SELECT timespan(period '(2000-01-01,2000-01-02]');
- timespan 
+SELECT duration(period '(2000-01-01,2000-01-02]');
+ duration 
 ----------
  1 day
 (1 row)
 
-SELECT timespan(period '[2000-01-01,2000-01-02)');
- timespan 
+SELECT duration(period '[2000-01-01,2000-01-02)');
+ duration 
 ----------
  1 day
 (1 row)
 
-SELECT timespan(period '(2000-01-01,2000-01-02)');
- timespan 
+SELECT duration(period '(2000-01-01,2000-01-02)');
+ duration 
 ----------
  1 day
 (1 row)
diff --git a/test/expected/01_period_tbl.test.out b/test/expected/01_period_tbl.test.out
index b37e7820c4..facd51d51e 100644
--- a/test/expected/01_period_tbl.test.out
+++ b/test/expected/01_period_tbl.test.out
@@ -9,31 +9,31 @@ COPY tbl_period_tmp FROM '/tmp/tbl_period' (FORMAT BINARY);
 COPY 100
 DROP TABLE tbl_period_tmp;
 DROP TABLE
-SELECT max(timespan(period(t, t + i))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i))) FROM tbl_timestamptz, tbl_interval;
    max    
 ----------
  01:39:00
 (1 row)
 
-SELECT max(timespan(period(t, t + i, true, true))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, true, true))) FROM tbl_timestamptz, tbl_interval;
    max    
 ----------
  01:39:00
 (1 row)
 
-SELECT max(timespan(period(t, t + i, true, false))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, true, false))) FROM tbl_timestamptz, tbl_interval;
    max    
 ----------
  01:39:00
 (1 row)
 
-SELECT max(timespan(period(t, t + i, false, true))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, false, true))) FROM tbl_timestamptz, tbl_interval;
    max    
 ----------
  01:39:00
 (1 row)
 
-SELECT max(timespan(period(t, t + i, false, false))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, false, false))) FROM tbl_timestamptz, tbl_interval;
    max    
 ----------
  01:39:00
@@ -774,8 +774,8 @@ SELECT upper_inc(p) FROM tbl_period;
  f
 (100 rows)
 
-SELECT timespan(p) FROM tbl_period;
- timespan 
+SELECT duration(p) FROM tbl_period;
+ duration 
 ----------
  00:07:00
  00:08:00
diff --git a/test/expected/05_periodset.test.out b/test/expected/05_periodset.test.out
index fad4f77f52..6a45923881 100644
--- a/test/expected/05_periodset.test.out
+++ b/test/expected/05_periodset.test.out
@@ -153,23 +153,59 @@ SELECT timespan(periodset '{(2000-01-01,2000-01-02),(2000-01-02,2000-01-03),(200
 SELECT timespan(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
  timespan 
 ----------
- 3 days
+ 5 days
 (1 row)
 
 SELECT timespan(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
  timespan 
 ----------
- 3 days
+ 5 days
 (1 row)
 
 SELECT timespan(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
  timespan 
 ----------
- 3 days
+ 5 days
 (1 row)
 
 SELECT timespan(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
  timespan 
+----------
+ 5 days
+(1 row)
+
+SELECT duration(periodset '{[2000-01-01,2000-01-01]}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(periodset '{(2000-01-01,2000-01-02),(2000-01-02,2000-01-03),(2000-01-03,2000-01-04)}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
+ duration 
 ----------
  3 days
 (1 row)
diff --git a/test/expected/05_periodset_tbl.test.out b/test/expected/05_periodset_tbl.test.out
index 89fa4ec945..95654e14de 100644
--- a/test/expected/05_periodset_tbl.test.out
+++ b/test/expected/05_periodset_tbl.test.out
@@ -223,6 +223,111 @@ SELECT timespan(ps) FROM tbl_periodset;
  timespan 
 ----------
  
+ 00:04:00
+ 01:21:00
+ 00:35:00
+ 00:02:00
+ 00:05:00
+ 00:24:00
+ 00:52:00
+ 00:37:00
+ 01:14:00
+ 01:45:00
+ 00:48:00
+ 00:37:00
+ 01:19:00
+ 00:20:00
+ 01:18:00
+ 00:14:00
+ 00:37:00
+ 01:25:00
+ 00:38:00
+ 00:41:00
+ 01:08:00
+ 00:49:00
+ 00:15:00
+ 00:24:00
+ 01:04:00
+ 01:17:00
+ 00:06:00
+ 01:19:00
+ 00:14:00
+ 00:12:00
+ 00:59:00
+ 00:56:00
+ 00:54:00
+ 01:43:00
+ 01:01:00
+ 01:09:00
+ 00:11:00
+ 01:07:00
+ 00:02:00
+ 00:34:00
+ 00:55:00
+ 00:22:00
+ 01:16:00
+ 00:20:00
+ 00:41:00
+ 00:31:00
+ 00:00:00
+ 01:03:00
+ 00:07:00
+ 00:12:00
+ 00:41:00
+ 00:20:00
+ 00:41:00
+ 00:58:00
+ 00:14:00
+ 00:23:00
+ 00:20:00
+ 00:49:00
+ 00:02:00
+ 00:23:00
+ 00:52:00
+ 00:13:00
+ 01:23:00
+ 00:14:00
+ 01:30:00
+ 00:58:00
+ 01:11:00
+ 00:29:00
+ 01:02:00
+ 00:03:00
+ 01:12:00
+ 00:33:00
+ 00:21:00
+ 01:12:00
+ 01:10:00
+ 00:31:00
+ 01:07:00
+ 01:22:00
+ 00:54:00
+ 01:18:00
+ 00:24:00
+ 01:08:00
+ 00:55:00
+ 00:58:00
+ 00:01:00
+ 01:42:00
+ 00:22:00
+ 00:31:00
+ 00:03:00
+ 00:31:00
+ 00:46:00
+ 00:16:00
+ 00:12:00
+ 00:41:00
+ 00:16:00
+ 00:07:00
+ 00:39:00
+ 00:35:00
+ 00:38:00
+(100 rows)
+
+SELECT duration(ps) FROM tbl_periodset;
+ duration 
+----------
+ 
  00:04:00
  00:40:00
  00:09:00
diff --git a/test/expected/21_tbox.test.out b/test/expected/21_tbox.test.out
index 53b5468ca8..333e7cd8d9 100644
--- a/test/expected/21_tbox.test.out
+++ b/test/expected/21_tbox.test.out
@@ -36,7 +36,7 @@ ERROR:  Could not parse TBOX: Both value and time dimensions are empty
 LINE 1: SELECT tbox 'TBOX((,),(,2000-01-01))';
                     ^
 SELECT tbox 'TBOX((AA, 2000-01-02))';
-ERROR:  Could not parse TBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT tbox 'TBOX((AA, 2000-01-02))';
                     ^
 SELECT tbox 'TBOX((1, AA))';
@@ -52,7 +52,7 @@ ERROR:  Could not parse TBOX: Missing opening parenthesis
 LINE 1: SELECT tbox 'TBOX((1, 2000-01-01),2, 2000-01-02))';
                     ^
 SELECT tbox 'TBOX((1, 2000-01-01),(AA, 2000-01-02))';
-ERROR:  Could not parse TBOX: Invalid input syntax for type double
+ERROR:  Invalid input syntax for type double
 LINE 1: SELECT tbox 'TBOX((1, 2000-01-01),(AA, 2000-01-02))';
                     ^
 SELECT tbox 'TBOX((1, 2000-01-01),(2, AA))';
@@ -141,7 +141,7 @@ SELECT ROUND(MAX(upper(b::floatrange) - lower(b::floatrange))::numeric, 6) FROM
  9.798705
 (1 row)
 
-SELECT MAX(timespan(b::period)) FROM tbl_tbox;
+SELECT MAX(duration(b::period)) FROM tbl_tbox;
    max    
 ----------
  00:09:00
diff --git a/test/expected/22_temporal.test.out b/test/expected/22_temporal.test.out
index 8487cdc86e..18063298af 100644
--- a/test/expected/22_temporal.test.out
+++ b/test/expected/22_temporal.test.out
@@ -1706,11 +1706,11 @@ SELECT appendInstant(tfloat 'Interp=Stepwise;{[1@2000-01-01, 1@2000-01-02)}', '2
 SELECT appendInstant(tfloat '{1@2000-01-01, 2@2000-01-02}', tfloat '2@2000-01-01');
 ERROR:  Timestamps for temporal value must be increasing: 2000-01-02 00:00:00+00, 2000-01-01 00:00:00+00
 SELECT appendInstant(tfloat '[1@2000-01-01, 1@2000-01-02]', '2@2000-01-02');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-02 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-02 00:00:00+00
 SELECT appendInstant(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]', tint '[1@2000-01-04, 1@2000-01-05]');
 ERROR:  The second argument must be of instant subtype
 SELECT appendInstant(tfloat '{[1@2000-01-01, 1@2000-01-02]}', '2@2000-01-02');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-02 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-02 00:00:00+00
 SELECT merge(tbool 't@2000-01-01', tbool 't@2000-01-02');
                         merge                         
 ------------------------------------------------------
@@ -2003,9 +2003,9 @@ SELECT merge(tint '{[2@2000-01-02], [1@2000-01-03, 2@2000-01-04]}', tint '[1@200
 SELECT merge(tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}', tint '{2@2000-01-03, 2@2000-01-04, 1@2000-01-05}');
 ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]', tint '[2@2000-01-03, 2@2000-01-04, 1@2000-01-05]');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(tint '{[1@2000-01-01, 2@2000-01-02, 1@2000-01-03],[1@2000-01-04, 1@2000-01-05]}', tint '{[2@2000-01-05, 2@2000-01-06, 1@2000-01-07],[1@2000-01-08, 1@2000-01-09]}');
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT merge(tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}', tint '{2@2000-01-02, 2@2000-01-03, 1@2000-01-04}');
 ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]', tint '[2@2000-01-02, 2@2000-01-03, 1@2000-01-04]');
@@ -2086,9 +2086,9 @@ ERROR:  Input values must be of the same interpolation
 SELECT merge(ARRAY[tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}', '{2@2000-01-03, 2@2000-01-04, 1@2000-01-05}']);
 ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(ARRAY[tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]', '[2@2000-01-03, 2@2000-01-04, 1@2000-01-05]']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-03 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(ARRAY[tint '{[1@2000-01-01, 2@2000-01-02, 1@2000-01-03],[1@2000-01-04, 1@2000-01-05]}', '{[2@2000-01-05, 2@2000-01-06, 1@2000-01-07],[1@2000-01-08, 1@2000-01-09]}']);
-ERROR:  The temporal values have different value at their overlapping instant 2000-01-05 00:00:00+00
+ERROR:  The temporal values have different value at their common instant 2000-01-05 00:00:00+00
 SELECT merge(ARRAY[tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}', '{2@2000-01-02, 2@2000-01-03, 1@2000-01-04}']);
 ERROR:  The temporal values have different value at their common instant 2000-01-03 00:00:00+00
 SELECT merge(ARRAY[tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]', '[2@2000-01-02, 2@2000-01-03, 1@2000-01-04]']);
@@ -3287,7 +3287,7 @@ SELECT timespan(tbool 't@2000-01-01');
 SELECT timespan(tbool '{t@2000-01-01, f@2000-01-02, t@2000-01-03}');
  timespan 
 ----------
- 00:00:00
+ 2 days
 (1 row)
 
 SELECT timespan(tbool '[t@2000-01-01, f@2000-01-02, t@2000-01-03]');
@@ -3299,7 +3299,7 @@ SELECT timespan(tbool '[t@2000-01-01, f@2000-01-02, t@2000-01-03]');
 SELECT timespan(tbool '{[t@2000-01-01, f@2000-01-02, t@2000-01-03],[t@2000-01-04, t@2000-01-05]}');
  timespan 
 ----------
- 3 days
+ 4 days
 (1 row)
 
 SELECT timespan(tint '1@2000-01-01');
@@ -3311,7 +3311,7 @@ SELECT timespan(tint '1@2000-01-01');
 SELECT timespan(tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}');
  timespan 
 ----------
- 00:00:00
+ 2 days
 (1 row)
 
 SELECT timespan(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]');
@@ -3323,7 +3323,7 @@ SELECT timespan(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]');
 SELECT timespan(tint '{[1@2000-01-01, 2@2000-01-02, 1@2000-01-03],[3@2000-01-04, 3@2000-01-05]}');
  timespan 
 ----------
- 3 days
+ 4 days
 (1 row)
 
 SELECT timespan(tfloat '1.5@2000-01-01');
@@ -3335,7 +3335,7 @@ SELECT timespan(tfloat '1.5@2000-01-01');
 SELECT timespan(tfloat '{1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03}');
  timespan 
 ----------
- 00:00:00
+ 2 days
 (1 row)
 
 SELECT timespan(tfloat '[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03]');
@@ -3353,13 +3353,13 @@ SELECT timespan(tfloat 'Interp=Stepwise;[1.5@2000-01-01, 2.5@2000-01-02, 1.5@200
 SELECT timespan(tfloat '{[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03],[3.5@2000-01-04, 3.5@2000-01-05]}');
  timespan 
 ----------
- 3 days
+ 4 days
 (1 row)
 
 SELECT timespan(tfloat 'Interp=Stepwise;{[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03],[3.5@2000-01-04, 3.5@2000-01-05]}');
  timespan 
 ----------
- 3 days
+ 4 days
 (1 row)
 
 SELECT timespan(ttext 'AAA@2000-01-01');
@@ -3371,7 +3371,7 @@ SELECT timespan(ttext 'AAA@2000-01-01');
 SELECT timespan(ttext '{AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03}');
  timespan 
 ----------
- 00:00:00
+ 2 days
 (1 row)
 
 SELECT timespan(ttext '[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03]');
@@ -3382,6 +3382,114 @@ SELECT timespan(ttext '[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03]');
 
 SELECT timespan(ttext '{[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03],[CCC@2000-01-04, CCC@2000-01-05]}');
  timespan 
+----------
+ 4 days
+(1 row)
+
+SELECT duration(tbool 't@2000-01-01');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tbool '{t@2000-01-01, f@2000-01-02, t@2000-01-03}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tbool '[t@2000-01-01, f@2000-01-02, t@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(tbool '{[t@2000-01-01, f@2000-01-02, t@2000-01-03],[t@2000-01-04, t@2000-01-05]}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(tint '1@2000-01-01');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(tint '{[1@2000-01-01, 2@2000-01-02, 1@2000-01-03],[3@2000-01-04, 3@2000-01-05]}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(tfloat '1.5@2000-01-01');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tfloat '{1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(tfloat '[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(tfloat 'Interp=Stepwise;[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(tfloat '{[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03],[3.5@2000-01-04, 3.5@2000-01-05]}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(tfloat 'Interp=Stepwise;{[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03],[3.5@2000-01-04, 3.5@2000-01-05]}');
+ duration 
+----------
+ 3 days
+(1 row)
+
+SELECT duration(ttext 'AAA@2000-01-01');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(ttext '{AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03}');
+ duration 
+----------
+ 00:00:00
+(1 row)
+
+SELECT duration(ttext '[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03]');
+ duration 
+----------
+ 2 days
+(1 row)
+
+SELECT duration(ttext '{[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03],[CCC@2000-01-04, CCC@2000-01-05]}');
+ duration 
 ----------
  3 days
 (1 row)
diff --git a/test/expected/22_temporal_tbl.test.out b/test/expected/22_temporal_tbl.test.out
index fd2ea411bf..080f7775d7 100644
--- a/test/expected/22_temporal_tbl.test.out
+++ b/test/expected/22_temporal_tbl.test.out
@@ -753,46 +753,46 @@ SELECT MAX(getTimestamp(inst)) FROM tbl_ttextinst;
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tbool;
    max    
 ----------
- 04:10:00
+ 05:39:00
 (1 row)
 
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tint;
    max    
 ----------
- 02:48:00
+ 04:01:00
 (1 row)
 
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tfloat;
    max    
 ----------
- 03:38:00
+ 04:55:00
 (1 row)
 
 SELECT MAX(timespan(getTime(temp))) FROM tbl_ttext;
    max    
 ----------
- 04:12:00
+ 05:34:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tbool;
+SELECT MAX(duration(period(temp))) FROM tbl_tbool;
    max    
 ----------
  05:39:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tint;
+SELECT MAX(duration(period(temp))) FROM tbl_tint;
    max    
 ----------
  04:01:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tfloat;
+SELECT MAX(duration(period(temp))) FROM tbl_tfloat;
    max    
 ----------
  04:55:00
 (1 row)
 
-SELECT MAX(timespan(period(temp))) FROM tbl_ttext;
+SELECT MAX(duration(period(temp))) FROM tbl_ttext;
    max    
 ----------
  05:34:00
@@ -801,25 +801,25 @@ SELECT MAX(timespan(period(temp))) FROM tbl_ttext;
 SELECT MAX(timespan(temp)) FROM tbl_tbool;
    max    
 ----------
- 04:10:00
+ 05:39:00
 (1 row)
 
 SELECT MAX(timespan(temp)) FROM tbl_tint;
    max    
 ----------
- 02:48:00
+ 04:01:00
 (1 row)
 
 SELECT MAX(timespan(temp)) FROM tbl_tfloat;
    max    
 ----------
- 03:38:00
+ 04:55:00
 (1 row)
 
 SELECT MAX(timespan(temp)) FROM tbl_ttext;
    max    
 ----------
- 04:12:00
+ 05:34:00
 (1 row)
 
 SELECT MAX(numSequences(seq)) FROM tbl_tboolseq;
diff --git a/test/queries/01_period.test.sql b/test/queries/01_period.test.sql
index a53688c615..670c27356f 100644
--- a/test/queries/01_period.test.sql
+++ b/test/queries/01_period.test.sql
@@ -93,11 +93,11 @@ SELECT upper_inc(period '(2000-01-01,2000-01-02]');
 SELECT upper_inc(period '[2000-01-01,2000-01-02)');
 SELECT upper_inc(period '(2000-01-01,2000-01-02)');
 
-SELECT timespan(period '[2000-01-01,2000-01-01]');
-SELECT timespan(period '[2000-01-01,2000-01-02]');
-SELECT timespan(period '(2000-01-01,2000-01-02]');
-SELECT timespan(period '[2000-01-01,2000-01-02)');
-SELECT timespan(period '(2000-01-01,2000-01-02)');
+SELECT duration(period '[2000-01-01,2000-01-01]');
+SELECT duration(period '[2000-01-01,2000-01-02]');
+SELECT duration(period '(2000-01-01,2000-01-02]');
+SELECT duration(period '[2000-01-01,2000-01-02)');
+SELECT duration(period '(2000-01-01,2000-01-02)');
 
 SELECT shift(period '[2000-01-01,2000-01-01]', '5 min');
 SELECT shift(period '[2000-01-01,2000-01-02]', '5 min');
diff --git a/test/queries/01_period_tbl.test.sql b/test/queries/01_period_tbl.test.sql
index 5de2f5bd04..42a75d6f42 100644
--- a/test/queries/01_period_tbl.test.sql
+++ b/test/queries/01_period_tbl.test.sql
@@ -36,11 +36,11 @@ DROP TABLE tbl_period_tmp;
 
 -------------------------------------------------------------------------------
 
-SELECT max(timespan(period(t, t + i))) FROM tbl_timestamptz, tbl_interval;
-SELECT max(timespan(period(t, t + i, true, true))) FROM tbl_timestamptz, tbl_interval;
-SELECT max(timespan(period(t, t + i, true, false))) FROM tbl_timestamptz, tbl_interval;
-SELECT max(timespan(period(t, t + i, false, true))) FROM tbl_timestamptz, tbl_interval;
-SELECT max(timespan(period(t, t + i, false, false))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, true, true))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, true, false))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, false, true))) FROM tbl_timestamptz, tbl_interval;
+SELECT max(duration(period(t, t + i, false, false))) FROM tbl_timestamptz, tbl_interval;
 
 SELECT tstzrange(p) FROM tbl_period;
 SELECT period(r) FROM tbl_tstzrange;
@@ -50,7 +50,7 @@ SELECT lower(p) FROM tbl_period;
 SELECT upper(p) FROM tbl_period;
 SELECT lower_inc(p) FROM tbl_period;
 SELECT upper_inc(p) FROM tbl_period;
-SELECT timespan(p) FROM tbl_period;
+SELECT duration(p) FROM tbl_period;
 SELECT shift(p, '5 min') FROM tbl_period;
 
 SELECT count(*) FROM tbl_period t1, tbl_period t2 WHERE period_cmp(t1.p, t2.p) = -1;
diff --git a/test/queries/05_periodset.test.sql b/test/queries/05_periodset.test.sql
index 629fc10633..ef5134a054 100644
--- a/test/queries/05_periodset.test.sql
+++ b/test/queries/05_periodset.test.sql
@@ -81,6 +81,13 @@ SELECT timespan(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(200
 SELECT timespan(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
 SELECT timespan(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
 
+SELECT duration(periodset '{[2000-01-01,2000-01-01]}');
+SELECT duration(periodset '{(2000-01-01,2000-01-02),(2000-01-02,2000-01-03),(2000-01-03,2000-01-04)}');
+SELECT duration(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
+SELECT duration(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
+SELECT duration(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
+SELECT duration(periodset '{[2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06]}');
+
 SELECT numPeriods(periodset '{[2000-01-01,2000-01-01]}');
 SELECT numPeriods(periodset '{(2000-01-01,2000-01-02),(2000-01-02,2000-01-03),(2000-01-03,2000-01-04)}');
 SELECT numPeriods(periodset '{(2000-01-01,2000-01-02),(2000-01-03,2000-01-04),(2000-01-05,2000-01-06)}');
diff --git a/test/queries/05_periodset_tbl.test.sql b/test/queries/05_periodset_tbl.test.sql
index 8e15fad2fe..33dc41979f 100644
--- a/test/queries/05_periodset_tbl.test.sql
+++ b/test/queries/05_periodset_tbl.test.sql
@@ -39,6 +39,7 @@ DROP TABLE tbl_periodset_tmp;
 SELECT memSize(ps) FROM tbl_periodset;
 SELECT period(ps) FROM tbl_periodset;
 SELECT timespan(ps) FROM tbl_periodset;
+SELECT duration(ps) FROM tbl_periodset;
 
 SELECT numPeriods(ps) FROM tbl_periodset;
 SELECT startPeriod(ps) FROM tbl_periodset;
diff --git a/test/queries/21_tbox.test.sql b/test/queries/21_tbox.test.sql
index c06d79c7ae..371249fed5 100644
--- a/test/queries/21_tbox.test.sql
+++ b/test/queries/21_tbox.test.sql
@@ -69,7 +69,7 @@ SELECT tbox 'TBOX((, 2000-01-01), (, 2000-01-02))'::period;
 -------------------------------------------------------------------------------
 
 SELECT ROUND(MAX(upper(b::floatrange) - lower(b::floatrange))::numeric, 6) FROM tbl_tbox;
-SELECT MAX(timespan(b::period)) FROM tbl_tbox;
+SELECT MAX(duration(b::period)) FROM tbl_tbox;
 
 -------------------------------------------------------------------------------
 -- Accessor functions
diff --git a/test/queries/22_temporal.test.sql b/test/queries/22_temporal.test.sql
index 30cf3bd5c4..b1d9c63091 100644
--- a/test/queries/22_temporal.test.sql
+++ b/test/queries/22_temporal.test.sql
@@ -915,6 +915,25 @@ SELECT timespan(ttext '{AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03}');
 SELECT timespan(ttext '[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03]');
 SELECT timespan(ttext '{[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03],[CCC@2000-01-04, CCC@2000-01-05]}');
 
+SELECT duration(tbool 't@2000-01-01');
+SELECT duration(tbool '{t@2000-01-01, f@2000-01-02, t@2000-01-03}');
+SELECT duration(tbool '[t@2000-01-01, f@2000-01-02, t@2000-01-03]');
+SELECT duration(tbool '{[t@2000-01-01, f@2000-01-02, t@2000-01-03],[t@2000-01-04, t@2000-01-05]}');
+SELECT duration(tint '1@2000-01-01');
+SELECT duration(tint '{1@2000-01-01, 2@2000-01-02, 1@2000-01-03}');
+SELECT duration(tint '[1@2000-01-01, 2@2000-01-02, 1@2000-01-03]');
+SELECT duration(tint '{[1@2000-01-01, 2@2000-01-02, 1@2000-01-03],[3@2000-01-04, 3@2000-01-05]}');
+SELECT duration(tfloat '1.5@2000-01-01');
+SELECT duration(tfloat '{1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03}');
+SELECT duration(tfloat '[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03]');
+SELECT duration(tfloat 'Interp=Stepwise;[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03]');
+SELECT duration(tfloat '{[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03],[3.5@2000-01-04, 3.5@2000-01-05]}');
+SELECT duration(tfloat 'Interp=Stepwise;{[1.5@2000-01-01, 2.5@2000-01-02, 1.5@2000-01-03],[3.5@2000-01-04, 3.5@2000-01-05]}');
+SELECT duration(ttext 'AAA@2000-01-01');
+SELECT duration(ttext '{AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03}');
+SELECT duration(ttext '[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03]');
+SELECT duration(ttext '{[AAA@2000-01-01, BBB@2000-01-02, AAA@2000-01-03],[CCC@2000-01-04, CCC@2000-01-05]}');
+
 SELECT period(tbool 't@2000-01-01');
 SELECT period(tbool '{t@2000-01-01, f@2000-01-02, t@2000-01-03}');
 SELECT period(tbool '[t@2000-01-01, f@2000-01-02, t@2000-01-03]');
diff --git a/test/queries/22_temporal_tbl.test.sql b/test/queries/22_temporal_tbl.test.sql
index 3994a82e9b..b33a0c8c08 100644
--- a/test/queries/22_temporal_tbl.test.sql
+++ b/test/queries/22_temporal_tbl.test.sql
@@ -219,10 +219,10 @@ SELECT MAX(timespan(getTime(temp))) FROM tbl_tint;
 SELECT MAX(timespan(getTime(temp))) FROM tbl_tfloat;
 SELECT MAX(timespan(getTime(temp))) FROM tbl_ttext;
 
-SELECT MAX(timespan(period(temp))) FROM tbl_tbool;
-SELECT MAX(timespan(period(temp))) FROM tbl_tint;
-SELECT MAX(timespan(period(temp))) FROM tbl_tfloat;
-SELECT MAX(timespan(period(temp))) FROM tbl_ttext;
+SELECT MAX(duration(period(temp))) FROM tbl_tbool;
+SELECT MAX(duration(period(temp))) FROM tbl_tint;
+SELECT MAX(duration(period(temp))) FROM tbl_tfloat;
+SELECT MAX(duration(period(temp))) FROM tbl_ttext;
 
 SELECT MAX(timespan(temp)) FROM tbl_tbool;
 SELECT MAX(timespan(temp)) FROM tbl_tint;