Hi Geoff:

your implementation of derived edges requires a convention
about where to put the arguments.
I was wondering which one you use. Let's assume we have a class
DJavaNaming which has a method lookup which returns a DJava-object.
lookup takes as argument a String-object. We would like to turn
lookup into a derived edge.

DJavaNaming = <lookup> DObject.

Now the get_lookup method will need to know where the argument is stored.
There are two natural possibilities where we can hide the argument:
in an immediate optional part of DJavaNaming or in an indirect
optional part.
Which one do you prefer?

In either case, when we want to do a traversal we will have to
make sure that the arguments are at the right places.

-- Karl