Blackboard Systems

Drawing on Nii's description [Nii86a, Nii86b] describe a blackboard system as a formal specialization of EventSystem. You may find it helpful to make the following simplifying assumptions:

• There are two kinds of components in a blackboard system: BBdata and ksources.
• The BBdata in the blackboard system are partitioned into a collection of layers.
• Each ksource is associated with some set of these layers.
• Each ksource has a method UpdateBB, which allows it to update the blackboard when it is invoked.
• When the data in a blackboard changes, for each layer that is changed the system announces the ChangedLayer event to each of the knowledge sources that are associated with that layer.

You need not say anything about the run time mechanisms involved in carrying out the updates. In particular, you don't have to say how the knowledge sources update the blackboard, or how new data is added to the blackboard.