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Re: "Humane Pointcut Languages" [Was: Re: [aspectj-users] AW:Pointcuton a constructor with a custom @Annotation] 
On 4/28/06, Dean Wampler <deanwampler@xxxxxxxxx> wrote:

On 4/27/06, Jonas Bonér <jonas@xxxxxxxxxxxxxxxxxx> wrote:
> I think Dean captures an important problem when he writes: "it bothers
> me that we discuss high-level concerns, say for example security, then
> turn around and write PCDs using very low-level primitives that tend
> to reference specific classes, methods, etc."

By the way, I should have added the word "only": "... using only very
low-level..." We'll always need those low-level primitives!

> But I can't see why a more verbose, java like syntax would be more
> "humane", and it for sure does not address the above stated problem.

You're right that I mixed two problems, general understandability and
appropriate levels of abstraction. I started with the easier problem,
understandability; what would be easier to read and therefore more
"humane"?

> I strongly believe that the only thing that helps is to raise the
> abstraction level above implementation details and rely on metadata.
>
> (A plus would of course be to have an optional simplified syntax that
> supports that directly, but with a goal to be more concise not
> verbose.)
>
> See my post http://jonasboner.com/2006/04/24/domain-driven-pointcut-design/,
> where I actually discussing another issue, but that is closely related
> to what I think is the main problem with having the wrong abstraction
> level.
>
> /Jonas

You make several great points in this blog. Contract4J only works
because its pointcuts use the principles you outline in your blog;
reliance on metadata annotations and avoidance of specific details of
class names, etc.


I would have liked to hear you talk at AOSD, will read the article.



I think the next major step for us is to further develop the concept
of interfaces in AOD, which will take us beyond the limitations of
what metadata annotations can provide, while still allowing us to
exploit the wonderful power of PCD languages like AspectJ's, without
some of the drawbacks.

Finally, I would like to emphasize a point that doesn't get enough
attention IMHO. The problems we're facing with pointcuts are really
examples of well-understood OOD principles. The fragile nature of
pointcuts that refer to specific details is an example of breaking the
Dependency Inversion Principle (DIP) and the Stable Dependencies
Principle (SDP), as described by Robert Martin
(objectmentor.com/resources/articles/dip.pdf and
objectmentor.com/resources/articles/stability.pdf).


That is an interesting observation that I think is very true.
Did we really think that we had to solve *new* problems? I guess that,
still "nothing is new under the sun", and that we are still "standing
on the shoulders of giants"... ;-)



Dean
http://www.aspectprogramming.com
http://www.newaspects.com
http://www.contract4j.org
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--
Jonas Bonér
Terracotta, Inc.

http://jonasboner.com
http://www.terracottatech.com

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