Abstract
Semantic issues connected with incomplete knowledge bases are discussed. In general, information incompleteness means the incom pleteness of given values in specified attribute domains, e. g., Codd's null value and Lipski's partial information. Another information in completeness connected with the lack of primary keys may also be considerable, and in this case the closed world assumption should not be assumed. This paper uniformly formulates these two types of in complete knowledge base and precisely defines interpretations of queries. In order to realize more intellectual questionanswering, some conditions that queries are not affected by the incompleteness are discussed.
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