Re: Completeness and Correctness of AspectJ Weaving

On 22 Jan 2009, at 15:52, G=FCnter Kniesel wrote:

> Pascal Costanza schrieb:
>> On 21 Jan 2009, at 20:21, DIMA MOHAMMED ALHADIDI wrote:
>>> Hi,
>>> Is AspectJ has a complete and correct weaving taking into  =

>>> consideration aspect interference and interaction?
>>> What I mean by completeness that every aspect advice must be  =

>>> applied at all the join points matched by the associated pointcut  =

>>> whereas what I mean by correctness that every aspect advice must  =

>>> be applied only at the join points that match the associated  =

>>> pointcut.
>> There is no such thing as an assurance that all aspects are  =

>> triggered at a specific join point. If several pieces of advice  =

>> apply at a join point, the first may, for example, throw an  =

>> exception, which means that the other ones are not called. Or, the  =

>> first may be a piece of around advice that doesn't proceed (or  =

>> worse, proceeds only conditionally). Etc.
>
> Pascal,
>
> you're right, an advice might do odd things so another one might
> never have a chance to execute.

I don't think throwing an exception is an odd thing to do.

Another typical example is a caching aspect, that looks up a result in  =

a cache if it was already computed, and only proceeds if it hasn't  =

been computed yet. This may interfere with an aspect that wants to  =

know how often a method has been called, for example (and where, for  =

example, it isn't clear whether it should count the invocations or the  =

actual computations, because the original developer didn't account for  =

the possibility that there could be a distinction between those two  =

cases).

> However, completeness and correctness *of aspect weaving* refer to
> a more basic level: Whether the advice is woven wherever it should
> and only there.

Of course.


Pascal

-- =

Pascal Costanza, mailto:[email protected], http://p-cos.net
Vrije Universiteit Brussel
Programming Technology Lab
Artificial Intelligence Lab
Pleinlaan 2, B-1050 Brussel, Belgium




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