Try to clarify design pattern.

chapters/classes.tex

@@ -1183,10 +1183,10 @@ \section{Balanced Models}\label{balanced-models}
 end BaseProperties;
 \end{lstlisting}
 
-The use of connector here is a special design pattern.
+The model \lstinline!BaseProperties! together with its use in derived classes and as component relies on a special design pattern defined below.
 The variables \lstinline!p!, \lstinline!h!, \lstinline!Xi! are marked as input to get correct equation count.
 Since they are connectors they should neither be given binding equations in derived classes nor when using the model.
-The design pattern is to give textual equations for them (as below); using \lstinline!connect!-equations for these connectors would be possible (and would work) but is not part of the design.
+The design pattern is to give textual equations for them (as below); using \lstinline!connect!-equations for these connectors would be possible (and would work) but is not part of the design pattern.
 
 This partial model defines that \lstinline!T!, \lstinline!d!, \lstinline!u! can be computed from
 the medium model, provided \lstinline!p!, \lstinline!h!, \lstinline!Xi! are given.  Every medium with