Knowledge organisation and reasoning

• The blackboard structure is highly structured.
• The blackboard prescribes the organisation of domain knowledge and all the input, intermediate and partial solutions needed to solve problems.
• The solution space is organised into one or more application-dependent hierarchies.
• Information at each level of the hierarchy represents partial solutions.
• Domain knowledge is partitioned into individual knowledge sources.
• Transformation in the blackboard hierarchy performed using algorithmic or heuristic procedure by interrogating knowledge modules under the control system.

Consider a group of people assembling a jigsaw with a blackboard:

• Volunteers look at their pieces and select most promising pieces and place then on the board.
• Each member would then look at his/her pieces and see if any fit those already on the board. Those with such pieces evolve the solution.
• The new solutions causes other pieces to fall into place and so on.

For the solution to be a blackboard solution:

• No direct communication is allowed to take place. The jigsaw could be assembled in total silence with no real problems.
• It would not matter who held what pieces.
• All communication is visual on the board.
• Each person is self-activating -- knowing when his/her pieces fit.
• No a priori order is established -- cooperation is mediated by state of solution on the blackboard.
• The solution is being assembled incrementally and opportunistically -- both important attributes of AI blackboard systems.

To illustrate the importance of the control systems consider one constrain in the above problem:

The blackboard lies in a narrow corridor so that only one person can view the board at a single instance.

• We now need some monitor to control how the board is viewed and the puzzle assembled.
• This can be quite simple or could involve a lot of complex strategies, such as viewing everybody's pieces and deciding which piece fits ``best''.
• Care will be needed so as not to compromise the one essential characteristic of a blackboard system, opportunistic problem solving.
• Computer implementations of blackboards often face similar problems.