Annotations which notify of changes

context: OAC (and SharedCanvas and IIIF) in web applications for manuscript
studies using linked open data structures.

*Annotation update notification service:*

Is there a place in a spec for an annotation which carries an endpoint with
it to notify about updates? Certainly not all annotation stores or
applications would honor this, but if they did it may improve the lives of
large repositories that share much of their data.

For example:
<anno> a oa:Annotation ;
eg:onUpdate "example.com/anno-notify" .

When someone (some machine) updates this annotation, the new annotation URI
can be sent to the endpoint where it would be consumed by some service so
the watcher would know something happened.

Perhaps for a cleaner world, there is a separate digital object that is a
Notifier like:
<Notifier> a eg:Notification ;
eg:watches <anno> ;
eg:onUpdate "example.com/anno-notify" ;
eg:onTargeted "example.com/anno-notify" ;
eg:onEmbodied "example.com/anno-notify" .

If I support it, I can look for these Notifiers on the graph when I make
changes or a store may register them independently if Stanford decides to
start following whose publicly using their manifests without just sending a
robot out for a stroll every once in an iteration.

I imagine a public annotation store can do this outside of standards
without too much grief, but it may be something an annotation generator (or
creator) would want to attach to an annotation regardless of the location.

Is this crazy or already possible? Events are closely tied to the
annotation objects developers create in web applications with great effect,
but to attach events/watchers to annotations in the wild may be a step too
far.

Patrick Cuba
Center for Digital Humanities
Saint Louis University