Merge pull request modelica#3090 from HansOlsson/ImproveSync

Improve sync

chapters/synchronous.tex

@@ -883,6 +883,13 @@ \subsection{Connected Components of the Equations and Variables Graph}\label{con
 \emph{Connected components}) of this graph with appropriate definition of
 the incidence operator.
 
+A special case is the built-in variable \lstinline!time! (see \cref{built-in-variable-time}).
+Each use of \lstinline!time! is conceptually included as a separate variable in this analysis, $\mathit{time}_i$ with $\text{\lstinline!der!}(\mathit{time}_{i}) = 1$.
+\begin{nonnormative}
+This means that \lstinline!time! can be used in different partitions without any restrictions.
+Additionally, it means that every partition directly referencing \lstinline!time! contains a call to \lstinline!der!.
+\end{nonnormative}
+
 \subsection{Base-Clock Partitioning}\label{base-clock-partitioning}
 
 The goal is to identify all clocked equations and variables that should
@@ -1050,9 +1057,11 @@ \section{Clocked Discretized Partition}\label{continuous-time-equations-in-clock
 \end{nonnormative}
 
 \begin{nonnormative}
-It is not defined, how events are handled that appear when solving the continuous-time partition. For example, a tool could handle events exactly in the same way as for a usual
-simulation.  Alternatively, relations might be interpreted literally, so that events are no longer triggered (in order that the time for an integration step is always the same,
-as needed for hard real-time requirements).
+It is not defined how to handle events that are triggered while solving the continuous-time partition.
+For example, a tool could handle events in the same way as for a usual simulation -- but only check them at the time associated with clock-ticks.
+
+Alternatively, relations might be interpreted literally, so that events are no longer triggered (in order that the time for an integration step is always the same, as needed for hard real-time requirements).
+However, even if relations do not generate events, when-clauses and operators \lstinline!edge! and \lstinline!change! should behave as normal.
 \end{nonnormative}
 
 From the view of the clocked partition, the continuous-time
@@ -1073,7 +1082,7 @@ \subsection{Clocked Discrete-Time and Discretized Continuous-Time}\label{clocked
 
 After sub-clock inferencing, see \cref{sub-clock-inferencing}, every partition that is associated to a clock has to be categorized as \willintroduce{clocked discrete-time} or \willintroduce{clocked discretized continuous-time} partition.
 
-If a clocked partition contains no operator \lstinline!der!, \lstinline!delay!, \lstinline!spatialDistribution!, no event related operators from \cref{event-related-operators-with-function-syntax} (with exception of \lstinline!noEvent!), and no \lstinline!when!-clause with a \lstinline!Boolean! condition, it is a \firstuse[clocked!discrete-time partition]{clocked discrete-time}\index{partition!clocked discrete-time} partition.
+If a clocked partition contains no operator \lstinline!der!, \lstinline!delay!, \lstinline!spatialDistribution!, no event related operators from \cref{event-related-operators-with-function-syntax} (with exception of \lstinline!noEvent! and \lstinline!smooth!), and no \lstinline!when!-clause with a \lstinline!Boolean! condition, it is a \firstuse[clocked!discrete-time partition]{clocked discrete-time}\index{partition!clocked discrete-time} partition.
 
 \begin{nonnormative}
 That is, the clocked discrete-time partition is a standard sampled data system that is described by difference equations.