Hi Boaz:

more implementation notes:

-- Karl
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Compatability

In the Demeter/C++ system we implemented the concept of compatibility
between traversal specifications and class graphs. Compatibility errors
proved to be a useful debugging tool for adaptive programs.
Therefore we generalize the concept to strategy graphs as follows:

>A strategy graph S is compatible with a class graph G, a name map N,
>and edge constraints B if for all strategy graph edges e of S there is
>a path P in G from s = N(Source(e)) to t = N(Target(e)) such that for
>every element [node or edge] x in P except for s and t, (B(e))(x) is
>true. [B(e) is the edge constraints of the strategy edge e, i.e. a
>predicate function mapping path elements to booleans.]

The idea behind compatability is to warn the user if there is a strategy
edge which does not define any path in the class graph.