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The Design and Implementation of CoBase

W. W. Chu, M. A. Merzbacher, L. Berkovich
Computer Science Department
University of California at Los Angeles


CoBase, a cooperative database, is a new type of distributed database that integrates knowledge base technology with database systems to provide cooperative (approximate and conceptual) query answering. Based on the database schema and application characteristics, data are organized into conceptual (type abstraction) hierarchies. The higher levels of the hierarchy provide a more abstract data representation than the lower levels. Generalization (moving up in the hierarchy), specialization (moving down in the hierarchy) and association (moving between hierarchies) are the three key operations in deriving cooperative query answers.

Relaxation in CoBase can also be specified explicitly in the query by the user or calling program through cooperative operators. We have extended SQL to CSQL by adding cooperative primitives. We describe the CoBase software implementation, including an inter-module data protocol that provides a uniform module interface. This modular approach provides flexibility in adding new relaxation modules and simplifies software maintenance.

CoBase uses LOOM as its knowledge representation and inference system and supports relational data bases (e.g. Oracle and Sybase). We have demonstrated the feasibility and functionality of CoBase on top of a Transportation Database. The CoBase methodology has also been adopted in the multi-media medical distributed database project at UCLA, which provides approximate query answers to medical queries.

Index Terms: Knowledge Representation, Type Hierarchy, Type Abstraction Hierarchy, Query Language, Query Rewrite, Cooperative Query Answering, Semantic Distance, Relaxation Control

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Tue Jun 21 15:42:52 PDT 1994