Queries

The original NPD SPARQL query set contains 25 queries obtained by interviewing users of the NPD dataset. Starting from the original NPD query set, we devised 30 queries having different degrees of complexity. The query set contains all the 21 queries from the version 1.1 of the benchmark, plus 8 queries with tree-witnesses in order to test the rewriting triggered by the existential in the RHS of OWL 2 QL ontologies.

The query set can be itself partitioned into 2 subsets:

• 9 Classically Optimizable Queries (that is, queries that can be translated into efficient SQL by using only information in mappings, ontology, and database dependencies)

• 21 Non-classically Optimizable Queries (that is, queries that require information from the data [e.g., dependencies not specified in the database schema] in order the be translated into efficient SQL queries)

The following table reports statistics for each query in the benchmark.

Queries Statistics

query |  #join  | #tw | #BGPs | # opts |  Agg |  Filt. |  Mod. |  
------|--------|-------|--------|-----|------------------|-------|-----|
**q1**  | 4  | 0 | 5 | 0 | N | Y | N | 
**q2**  | 5  | 0 | 6 | 0| N| Y | N| 
**q3**  | 3  | 0 | 4 | 0| N| Y| Y |
**q4**  | 5  | 0 | 6 | 0| N| Y| Y |
**q5**  | 5  | 0 | 6 | 0| N| Y| Y  |  
**q6**  | 6  | 0 | 7 | 0| N| Y| Y |
**q7**  | 7  | 0 | 8 | 0| N| Y| N |
**q8**  | 3  | 0 | 4 | 0| N| Y| N |
**q9**  | 3  | 0 | 4 | 0| N| Y| Y |
**q10** | 2  | 0 | 3 | 0| N| Y| Y |
**q11** | 7  | 0 | 8 | 0| N | Y| Y|
**q12** | 8  | 0 | 10 | 0| N | Y| Y|
**q13** | 2  | 0 | 3 | 2| N| Y| N |
**q14** | 2  | 0 | 5 | 2| N| Y| N  |
**q15**  | 4  | - | 5 | 0| Y| Y| N |
**q16**  | 3  | - | 3 | 0| Y| Y | N |
**q17**  | 8  | - | 8 | 0| Y | N | Y |
**q18**  | 4  | - | 5 | 0| Y | N| N |
**q19**  | 8  | - | 8 | 0| Y| N| N |
**q20**  | 3  | - | 3 | 0 | Y| N| N |
**q21**  | 3  | - | 3 | 0| Y| N| N|
**q22**  | 1  | 1 | 2 | 0| N| N| N|
**q23**  | 2  | 1 | 3 | 0| N| N| N|
**q24**  | 2  | 1 | 3 | 0| N| N| N|
**q25**  | 1  | 1 | 1 | 0| N| N| N|
**q26**  | 2  | 1 | 1 | 0| N| N| N|
**q27**  | 1  | 1 | 2 | 0| N| N| N|
**q28**  | 2  | 1 | 3 | 0| N| N| N|
**q29**  | 4  | 1 | 5 | 0| N| N| N|
**q30**  | 6  | 1 | 7 | 0| N| N| N|

Legenda

• #join: Total number of JOIN operators
• #tw: Number of tree-witnesses
• max(#subcls): Maximum number of subclasses (resp., subrole) for a concept (resp., role) in the query
• opt: Number of optionals
• Agg: Aggregates Y es or N o
• Filt: Filters Y es or N o
• Mod: Modifiers Y es or N o

Classically Optimizable Queries

The queries in this set are q1,q2,q3,q4,q5,q7,q8,q25. These queries

• Do not contain OPTIONAL.
• Do admit an efficient (that is, a small number of SPJ queries) translation that is logically derivable without resorting to the data stored in the physical source (but by using the database dependencies explicitly specified in the database schema).

Query q1

What are the licences, what is the interest applied to the respective licensees, and from when are them valid?

PREFIX npdv: <http://sws.ifi.uio.no/vocab/npd-v2#>

SELECT DISTINCT ?licenceURI ?interest ?date
WHERE {
    ?licenceURI a npdv:ProductionLicence .   		
    [ ] a npdv:ProductionLicenceLicensee ;
      	npdv:dateLicenseeValidFrom ?date ;
      	npdv:licenseeInterest ?interest ;
      	npdv:licenseeForLicence ?licenceURI .   
   FILTER(?date > "1979-12-31T00:00:00"^^xsd:dateTime)	
}

Query q2

Who are the operators for licences whose contracts were started after 1980?

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX npdv: <http://sws.ifi.uio.no/vocab/npd-v2#>

SELECT ?licenceURI ?company ?date
WHERE {
   ?licenceURI a npdv:ProductionLicence .
      [ ] a npdv:ProductionLicenceOperator ;
      npdv:dateOperatorValidFrom ?date ;
      npdv:licenceOperatorCompany [ npdv:name ?company ] ; 
      npdv:operatorForLicence ?licenceURI .
    FILTER(?date > "1979-12-31T00:00:00"^^xsd:dateTime)
} ORDER BY ?licenceURI

Query q3

What are the licences whose expiration dates were after 1980?

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX npdv: <http://sws.ifi.uio.no/vocab/npd-v2#>

SELECT ?licence ?dateGranted ?dateValidTo
WHERE {
   [ ] a npdv:ProductionLicence ;
      npdv:name ?licence ;
      npdv:dateLicenceGranted ?dateGranted ;
      npdv:dateLicenceValidTo ?dateValidTo .
      FILTER(?dateValidTo > "1979-12-31T00:00:00"^^xsd:dateTime)
} ORDER BY ?licence

Non-classically Optimizable Queries

This set of queries contains all the queries with tree-witnesses (that is, queries which require the full reasoning in OWL 2 QL for the answers to be complete)

Query q6

This is a query that asks for the wellbores, their length, and the companies that completed the drilling of the wellbore after 2008, and sampled more than 50m of cores.

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX npdv: <http://sws.ifi.uio.no/vocab/npd-v2#>

SELECT ?licence ?dateGranted ?dateValidTo
WHERE {
   [ ] a npdv:ProductionLicence ;
      npdv:name ?licence ;
      npdv:dateLicenceGranted ?dateGranted ;
      npdv:dateLicenceValidTo ?dateValidTo .
      FILTER(?dateValidTo > "1979-12-31T00:00:00"^^xsd:dateTime)
} ORDER BY ?licence