Reference: Nii, H. P. Blackboard Systems. 1986.
Abstract: The first blackboard system was the HEARSAY-II speech understanding system , that evolved between 1971 and 1976. Subsequently, many systems have been built that have similar system organization and run-time behavior. The objectives of the document are: (1) to define what is meant by "blackboard systems", and (2) to show the richness and diversity of blackboard system designs. The article begins with a discussion of the underlying concept begind all blackboard systems, the blackboard model of problem solving. In order to bridge the gap between a model and working systems, the blackboard framework, and extension of the basic blackboard model is introduced, including a detailed description of the model's components and their behavior. A model does not come into existence on its own and is usually an abstraction of many examples. In Section 2, the history of ideas is traced and the designs of some application systems that helped shape the backboard model are detailed. We then describe and contrast existing blackboard systems. Blackboard systems can generally be divided into two categories; application and skeletal systems. In application systems the blackboard system components are integrated with the domain knowledge required to solve the problem at hand. Skeletal systems are devoid of domain knowledge, and, as the name implies, consist of the essential system components from which application systems can be built by the addition of knowledge and the specification of control (i.e. meta-knowledge). Application systems will be discussed in Section 3, and skeletal systems will be discussed elsewhere. In Section 3.6, we summarize the features of the application systems and in Section 4 present the author's perspective on the utility of the blackboard approach to problem solving and knowledge engineering.