Default extensions: dealing with computer information

摘要

A conditional knowledge base may be sometimes analyzed as a union of several pieces of information that are provided by independent sources. In this case, it is possible to extend separately each of these subbases via their rational closure, and then glue the results together to get a rational extension of the whole base, in which the specificity of its components is taken into account. The resulting inference relation is free from the undesirable and counterintuitive results that can be encountered in the Z-system, Lex-system or W-system.