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<h3 align="center">AspectJ Language Design</h3>
<h4>AspectJ 1.2 Language Features</h4>
<ul>
<li>Extensible pointcuts, abstract pointcuts, and interfaces<ul>
<li>
<a href="http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg00458.html">
http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg00458.html</a></li>
<li>
<a href="http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg00467.html">
http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg00467.html</a> <br>
</li>
</ul>
</li>
</ul>
<h4>Key Language Design Properties (from Gregor)</h4>
<p>(1) Orthogonal join point model - the different kinds of join points, the
different primitive pointcuts, and the different kinds of advice can be used in
any combination.</p>
<p>This was one of the hardest parts of the design to get right, because of the
"constructor must call super" rule in Java. But we finally got this in 1.0.<br>
<br>
(2) Pointcuts support composition and abstraction. Abelson and Sussman say that
composition and abstraction are the key elements of a real language. Clearly the
pointcut mechanism is the new thing in AspectJ, and so it was critical that it
support composition and abstraction. The fact that someone can write:</p>
<blockquote>
<p><font face="Courier">/* define an abstraction called stateChange */<br>
pointcut stateChange(): call(void FigureElement+.set*(*));<br>
<br>
/* compose pointcuts to get other pointcuts */<br>
pointcut topLevelStateChange(): stateChange() `<br>
&& !cflowbelow(stateChange());</font></p>
</blockquote>
<p>is what makes it possible for people to really work with crosscutting
structure and make their code more clear.<br>
<br>
(3) Statically type checked. The efficiency, code quality and programmer
productivity arguments for this have been made elsewhere, so I won't repeat
them. <br>
<br>
(4) Efficient. AspectJ code is as fast as the equivalent functionality, written
by hand, in a scattered and tangled way.<br>
<br>
(5) Simple kernel. I've heard some people say that AspectJ is too big and too
complex. In the most important sense of simple AspectJ is simple. I can reason
about any AspectJ program with a simple model. The kernel of AspectJ is simple,
and the orthogonality described above means that its easy to start with just the
kernel and slowly add to that.</p>
<p>Its pretty clear to pull out this kernel of AspectJ. I would argue that the
right idea for a standard AOP API<br>
is this kernel, packaged in a way that allows building more sophisticated tools
on top of it.<br>
<br>
(6) Supports multiple weave times. AspectJ is neutral on whether weaving happens
at pre-process, compile, post-process, load, JIT or runtime. This neutrality is
critical. Its why there are serious JVM experts who are already thinking about
JVM support for AspectJ.</p>
<p>There's more, but I think these are the most important ones. I think any
functionality this group comes up with should also meet these criteria.<br>
</p>
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