| 摘要 |
A tool is used for knowledge engineers for building and interpreting a knowledge base having separate portions encoding control knowledge, factual knowledge, and judgmental rules. The tool has an inference engine applying the judgmental rules according to a built-in control procedure defining discrete states or control steps during a consultation with a user. The control knowledge is encoded in an applicative and imperative language defining control actions to be executed during interruption of the built-in control procedure at specified control steps. Since the control knowledge is explicit and results in the modification of data only in a precisely defined fashion, the tool can be used to build knowledge systems that can always explain their conclusions and reasoning, and that are intelligible and modifiable. To provide transparent representation of control knowledge as well as factual knowledge, the knowledge base is preferably organized into distinct frames which include the rules; control blocks separately encoding the control knowledge; and classes which become instantiated, attributes which take on values describing the class instances, class types, legal value hierarchies, and user-defined functions, which all encode factual knowledge. The knowledge engineer may provide control blocks to be executed at the start of the consultation, after the instantiation of specified classes, when a value for a specified attribute is to be determined, after a specified attribute is determined, and upon explicit invocation by another control block. The tool can also implicitly determine subsumed attributes.
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