The blackboard pattern is arguably the least known among our first group. This is a pattern that is not common because it is best used with some specialized tasks. However, you may be familiar with it if you work in speech recognition, vehicle tracking, sonar signals interpretation, or similar open-ended forms of searching and matching.
The Blackboard Pattern Defined
Three appears to be the magic number for parts of an architectural pattern. Likewise, this pattern again has three concepts that make it up. There is the blackboard, the knowledge source, and the control. These parts work together to match data to a solution.
The Blackboard pattern uses the idea of a blackboard as a place to hold global data. We can inspect or update the blackboard. A knowledge source can update the blackboard, and we can have multiples of these. Then, the control works with multiple sources and interacts with the sources and the blackboard. The control effectively loops through sources looking for a solution and then posts that solution once found. Thus, this approach allows us to quickly match known solutions or expand available solutions when a new one is needed.
