Reference: Chaudhri, V. K.; Farquhar, A.; Fikes, R.; Karp, P. D.; & Rice, J. P. Open Knowledge Base Connectivity 2.0. Knowledge Systems Laboratory, January, 1998.
Abstract: This document specifies a protocol for accessing knowledge bases (KBs) stored in knowledge representation systems (KRSs). By KRS we mean both systems that would traditionally be considered KRSs, as well as can be viewed as a KRS, for example, an object-oriented database. The protocol, called the Open Knowledge Base Connectivity (OKBC), provides a set of operations for a generic interface to underlying KRSs. The interface layer allows an application some independence from the idiosyncrasies of specific KRS software and enables the development of generic tools (e.g., graphical browsers and editors) that operate on many KRSs. OKBC implementations exist for several programming languages, including Java, C (client implementation only), and Common Lisp, and provide access to KBs both locally and over a network.
OKBC is complementary to language specifications developed to support knowledge sharing. KIF , the Knowledge Interchange Format, provides a declarative language for describing knowledge. As a pure specification language, KIF does not include commands for knowledge base query or manipulation. Furthermore, KIF is far more expressive than most KRSs. OKBC focuses on operations that are efficiently supported by most KRSs (e.g., operations on frames, slots, facets -- inheritance and slot constraint checking). OKBC is intended to be well impedance-matched to the sorts of operations typically performed by applications that view or manipulate object-oriented KRSs.
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