I don���t know about performance, but as far as I understand you can also subscribe to ���WindowAnnouncement withAllSubclasses���.
That would be setting yourself up for a heap of duplicates.
By design, you can subscribe twice to the same announcement and receive two notifications, so doing that will net you $InheritanceLevelsFromWindowAnnouncement copies of each���
My point was that maybe instead of making an implicit inheritance subscription we should make it explicit. So if you want to subscribe only to WindowAnnouncement and not to its subclasses, you can do that. If you wan to subscribe to the hierarchy you can do ���WindowAnnouncement withAllSubclasses���. Again, this is just an idea and I don���t know how it impacts performance or some other things. I just see a limitation now that I cannot subscribe only to a class ignoring it subclasses without doing a check later.
Uko