Make Figure title optional as decided at the 101th design meeting (mo…

…delica#2580)

chapters/annotations.tex

@@ -78,7 +78,7 @@ \subsection{Annotations for Figures}\doublelabel{annotations-for-figures}
 The \lstinline!figure-annotations! is a list of \lstinline!Figure! annotations given by:
 \begin{lstlisting}[language=modelica]
 record Figure
-  String title "Title meant for display";
+  String title = "" "Title meant for display";
   String identifier "Identifier meant for programmatic access";
   String group = "" "Name of plot group";
   Boolean preferred = false "Automatically display figure after simulation";
@@ -103,15 +103,14 @@ \subsection{Annotations for Figures}\doublelabel{annotations-for-figures}
 \autoref{plot-curves}, that all share a common x and y axis with properties
 described in \autoref{axis-properties}.
 
-The \lstinline!title! of a \lstinline!Figure! shall be non-empty and is
-mandatory, as every figure needs a title for presentation in contexts such as a
-list of figures, and as it is generally hard for tools to automatically generate
-a meaningful title.  On the other hand, when the \lstinline!title! of a
-\lstinline!Plot! isn't provided, the tool produces a default, but the default is
-allowed to be empty.  Providing the empty string as \lstinline!title! of a
-\lstinline!Plot! means that no title should be shown.  The plot title is not to
-be confused with the plot \emph{label} which is never empty, see below. Variable
-replacements, as described in \autoref{variable-replacements}, can be used in the
+Both \lstinline!Figure! and \lstinline!Plot! can have an optional title. When
+the \lstinline!Figure! \lstinline!title! is the empty string (the default), the
+tool must produce a non-empty title based on the figure content.  On the other
+hand, the \lstinline!Plot! \lstinline!title! has a tool-dependent default, but
+the default may be the empty string.  When the Plot title is the empty string, no
+title should be shown. The plot title is not to be confused with the plot
+\emph{label} which is never empty, see below. Variable replacements, as
+described in \autoref{variable-replacements}, can be used in the
 \lstinline!title! of \lstinline!Figure! and \lstinline!Plot!.
 
 The \lstinline!identifier! in \lstinline!Figure! and \lstinline!Plot! is an