Model Extensions

Daniel Vainsencher danielv at
Thu Jan 31 11:59:44 UTC 2008

Your changes sound like valuable infrastructure, not only for model 
extensions. To help them get included, I suggest you introduce them in 
small, well explained pieces. Note that classes are rather tricky 
objects, and class changes are tricky operations. Be careful... have tests.


Matthew Fulmer wrote:

>> [1]
> On page 22 of this paper, you mentioned that the notification
> mechanism should tell you the previous values of classes and
> methods for the purpose of cache invalidation. 
> Goran and I made just these changes to SystemChangeNotifier in
> Squeak as part of our DeltaStreams project; now, when classes,
> methods, and class comments are changed, a notification with both
> the old and new version is sent. It is completely
> backward-compatible with the old SystemChangeNotifier protocol,
> as far as we can tell:
> In the future (a month or two), I'm going to augment the
> notifier again to support grouping of related changes, such as
> all changes involved in loading a package, filing-in a
> changeset, or loading a bug-fix, so that the enhanced logging
> features of DeltaStreams can show system changes at more the
> level the user made them; loading a package was a single-action
> to them; the log should show it as a single action.

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