| 摘要 |
A frame-based knowledge representation system is built on a relational database that is completely transparent to the user. A user at a client machine sends standard knowledge base queries across a distributed computer system and the system translates the queries into a language suitable for querying the database, such as Structured Query Language (SQL). The system stores a hierarchical data model that includes classes, particular instances of the classes, and relations among the classes and instances. Primitive objects, such as classes and instances, are organized with their associated attributes into frames. The system consists of three main tables and auxiliary tables. The frames table stores frames with associated slots and values, along with associated ownerships, access permissions, and other facets. The superclass-set table stores the frames and associated superclasses or ancestor classes. The third table, the classes table, stores class frames, slots, and values, and a slot type designating a slot as own or template. The database also includes tables for security definitions, logging, and other features. To query the knowledge base, the user submits a query, preferably according to the Open Knowledge Base Connectivity protocol, and the system translates the query into SQL. The result is formatted and processed to check user permissions before being returned to the user over the computer network. The system is accessed through a variety of interfaces, including a Web browser and various application programming interfaces.
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