the notion of tables proposed by Imielinski and Lipski [1984]. We do not dis-
cuss updates on incomplete-information databases in any detail in this paper.
However, their semantics for updates is related to the semantics of DLP, and
some of their ideas are applicable to its implementation. Wilkins [1986] also
has a theory of updates based on a possible world semantics. Her assumptions
and development are considerably different from ours—for example, she sup-
ports the insertion of arbitrary formulas in the database. Abiteboul and Vianu
[1987] have proposed a procedural language for writin ...
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