[PRL] AOP questions

[Doug Orleans]

John Clements writes:
 > This seems sad, to me, because abstraction as 
 > functional programmers understand it is all about modeling procedures 
 > as relations from inputs to outputs, not as sequences of execution 
 > states.

I think AOP advocates might say that purely functional decomposition
of a program isn't able to cleanly modularize some kinds of concerns,
so it's better to have some other ways of looking at the program in
addition to just functionally, such as classes or aspects.  Also, it's
usually more about the level of organization above procedures, not so
much how to model procedures themselves.  (Maybe it would help if you
thought of an aspect as being like a functor/unit?  Have you read the
Jiazzi papers?)

 > 2) "Join Points":
 > 	It appears to me that join points are not truly points, but are rather 
 > contiguous subsequences.  I say this because of the existence of things 
 > like "around" and "after" pcds, which don't make sense for a definition 
 > of join points as single points in a program's execution.  Is this 
 > fair?

"around" and "after" are kinds of advice, not kinds of pointcuts.  Or
maybe they sit somewhere in between.  They're sort of like
combinators-- they say how to put together a join point with its
advice.  (In Socrates, "around" is just a way of affecting advice
precedence, and "before" and "after" are just macros for "begin" and
"begin0".)

--Doug

P.S. Not all AOP methodologies are about dynamic join points,
e.g. points in the program execution; some are about static join
points, e.g. points in the program expression.  So I don't think it's
accurate to say that "AOP insists on modeling evaluation as a series
of execution states", because some AOP doesn't model execution at all.