Turning The Partial-Closed World Assumption Upside Down
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The partial-closed world setting provides an intermediate ground between open-world and closed-world settings. Previous work on the partial-closed world assumption assumes that incompleteness is the default, i.e., that databases in general can be incomplete, and are only definitely complete in specified parts. In this work we turn this assumption around, and study databases where completeness is the default, and incompleteness only occurs in specified parts. We present four languages for describing potentially incomplete parts of databases, full-table statements, patterns, local statements and query statements.We show that except for full-table statements, it is not possible to translate between the two settings without extending the languages. Finally, we present techniques to decide query completeness entailment for each of the languages both on the schema and instance level, finding that for queries under bag semantics, the complexity is sometimes easier than under the setting where complete parts are specified. Copyright © 2016 for the individual papers by the papers's authors.