While a Registry is similar to a Blackboard in that they are both flexible
repositories of information, there are some subtle differences:
- The Registry is a bit more structured (values are Lists as opposed to
general Objects).
- There is only one Registry, whereas there are Blackboards on several
different levels (the Workbench Blackboard, the Task Blackboard, the Layer
Blackboard, the LayerViewPanel Blackboard), thus representing varying degrees
of scope.
- Registry keys are in general "well known" to a greater degree than
Blackboard keys, which plugins tend to create as needed. Thus the Registry
can be thought of as being more static, and the Blackboard more fluid.
- Registry entries are intended to be much more static than Blackboard
entries. You might well think about persisting a Registry, but probably never
a Blackboard
- In the bigger world, Registries have all kinds of security,
classification and lifecyle features that probably would not appear on a
Blackboard.