[PRL] AOP questions

[Doug Orleans]

John Clements writes:
 > IIUC, I believe that the graph by itself will not be sufficient to 
 > represent an evaluation.  That is, I think that an evaluation will have 
 > to be represented as graph + traversal.

By traversal do you just mean a total ordering of the edges?  I was
assuming that was intrinsic to the graph, i.e. each node has an
ordered list of outgoing edges, and the graph is traversed depth-first.

 > Forgive my ignorance: can you explain, in the model you're describing, 
 > what a node in the graph represents and what edges represent?  Is the 
 > store off on the side?  Is your picture of the world big-step or 
 > small-step?

The nodes are join points (activation records? stack frames?) and the
edges are procedure calls.  The store is not represented, this is just
the control-flow graph.  I guess this is small-step?  Evaluating an
application expression steps you across one edge in the graph.

Maybe you should also have a back-edge representing the return from B
to A, and a continuation invocation wouldn't have this back-edge.  I
admit I'm a little fuzzy here, but surely someone has thought about
continuations from a graph perspective and has a better story for
this?

--Doug