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Databases in real life are often neither entirely closed-world nor entirely open-world. Indeed, databases in an enterprise are typically partially closed, in which a part of the data is constrained by master data that contains complete information about the enterprise in certain aspects. It has been shown that despite missing tuples, such a database may turn out to have complete information for answering a query. This paper studies partially closed databases from which both tuples and values may be missing. The authors specify such a database in terms of conditional tables constrained by master data, referred to as c-instances.
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