Scone Knowledge Base Scott E. Fahlman April 14, 2005 School of Computer Science

April 14, Goals for Scone Build a practical “knowledge base” (KB) engine and toolkit that can be used in any number of applications. Semantic network model: nodes are entities, links are statements. Emphasis on scalability and ease of use. –A few million entities and relations on a high-end workstation. –Parallelizable if you want more. Implemented in Common Lisp, runs on 32-bit or 64-bit workstations. Will release as open-source, with a tutorial book. Alicia Tribble (Ph.D. student) working on NL input of knowledge.

April 14, Current Cabilities Multiple-inheritance hierarchy with exceptions. Efficient detection of type violations. Mapping of concepts to words is many-to-many. User-defined roles and relations. Can attach meta-knowledge to any node or link. Multiple contexts: hierarchical & lightweight. Can represent numerical weights and probabilities. Programmer-level document. Current “core” KB is minimal. Machinery for episodic memory exists, but is minimal.

April 14, Multiple Contexts Each link (statement) in SCONE is tied to the context in which it is true. Contexts form an inclusion hierarchy. Each starts as a clone, then adds or cancels some information. To activate a context, mark it and all included contexts, then mark all active statements. Only these link are active. So multiple contexts are efficient, lightweight, and heavily used for reasoning about alternative states of the universe, real or hypothetical. (“What if…”) The multiple-context mechanism is used to implement actions and events.