I sent the following note to Vassili Bykov shortly after his first blog item Introducing Announcements, a replacement system for the Events system of VisualWorks.

Thanks for the blog items on Announcements. As you know, I am in favor of reifying the parts of Smalltalk that are now not very object-oriented. (Another area is that of protocols.) I

I hope you will also cover how Announcements are connected to the classes that trigger them (similar to the use of #constructEventsTriggered for events) along with any possibilities of inheritance and overriding.

A particular requirement of SmalltalkDoc is to be able to lists the announcements defined by a specific class. For events, it currently sends #constructEventsTriggered to the class and separately to its superclass, and then subtracts out the superclass events. This works, but separate #allAnnouncements and #definedAnnouncements methods would be better.

These days, Vassili is busy working on the latest release of VisualWorks, so he probably hasn't had to time to consider this further. This has given me time to think about the issue I raised a bit deeper.

SmalltalkDoc, a comprehensive documentation subsystem Mark Roberts and I have been working on (as resources permit), needs to be able to document the list of Announcements that objects of ClassX announce. Why? So that programmers know what announcements from ClassX objects they can subscribe to and handle -- without having to pour through the code of ClassX. That's why something like #constructEventsTriggered is needed for Announcements, too.

But there is a deeper reason than just for documentation. In a word, it is reflectivity , a fundamental property of Smalltalk , the ability of programs to get information about themselves and work with it. This is particularly valuable for the creation of tools. For example, suppose someone wanted to create tools that help programmers bridge the gap between Pollock UI panes and the objects of a domain model. It would be necessary to tell them about UI pane announcements. The Parts subsystem of the old Visual Smalltalk product is an example of this. Who knows what other tools could also take advantage of this information.