Cooperating heterogeneous systems: a blackboard-based meta approach
David Gary Schwartz · OhioLink ETD Center (Ohio Library and Information Network) · 1993
It is increasingly the case that organizations rely upon diverse computer systems to perform a variety of knowledge-based tasks. This not only presents technical issues of interoperability and integration, but philosophical issues of how cooperation and interaction between computational entities is to be realized. Cooperating systems are systems that work together toward a common end. To develop cooperating heterogeneous systems the technical and philosophical must find common ground. The concepts of cooperation must find realization in technically sound system architectures. The heterogeneity and complexity of knowledge sources make it difficult to design and use an integrated system. This is particularly true of systems that are constructed of pre-existing components, each of which has its own task, design, and structure. We advocate adding a uniform meta-layer between knowledge sources and the rest of the system. The layer consists of a family of interpreters, one for each knowledge source, and meta-knowledge. A system architecture to integrate and control diverse knowledge sources is presented. The architecture is based on the meta-level properties of the logic programming language Prolog. We describe an implementation of the architecture, a Framework for Logic Programming Systems with Distributed Execution (FLiPSiDE). Based on the vanilla blackboard interpreter, we present interpreter enhancements that model the cooperative behavior of knowledge sources. Examples of interpreters to handle shared semantics and multiple interaction behaviors are shown. We introduce a dedicated trigger handler knowledge source to the design of control blackboard architectures. The advantages of such a knowledge source, including dynamic modification of triggers, are described. The support of human users is presented as an example of integrating heterogeneous users with the computational knowledge sources. The FLiPSiDE architecture is generalized to create a distributed Prolog environment. As background we present the blackboard model and some of its realizations, explain the concepts of meta-level systems, and examine organizational learning and decision making to determine the essential characteristics of cooperation.