Belnap-Dunn logic and query answering in inconsistent databases with null values

03/09/2023

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by   C. A. Middelburg, et al.

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This paper concerns an expansion of first-order Belnap-Dunn logic, named BD^⊃,𝖥, and an application of this logic in the area of relational database theory. The notion of a relational database, the notion of a query applicable to a relational database, and several notions of an answer to a query with respect to a relational database are considered from the perspective of this logic, taking into account that a database may be an inconsistent database or a database with null values. The chosen perspective enables among other things the definition of a notion of a consistent answer to a query with respect to a possibly inconsistent database without resort to database repairs. For each of the notions of an answer considered, being an answer to a query with respect to a database of the kind considered is decidable.