A useful four-valued database logic
| Autor: | Gösta Grahne, Ali Moallemi |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
060201 languages & linguistics
SQL Database Computer science Relational database Cylindric algebra 06 humanities and the arts 02 engineering and technology Intuitionistic logic computer.software_genre Query language Constructive Negation Null (SQL) 0602 languages and literature 0202 electrical engineering electronic engineering information engineering 020201 artificial intelligence & image processing computer computer.programming_language |
| Zdroj: | IDEAS |
| DOI: | 10.1145/3216122.3216157 |
| Popis: | Recently there has been an effort to solve the problems caused by the infamous NULL in relational databases, by systematically applying Kleene's three-valued logic to SQL. The third truth-value is unknown. In this paper we show that by using a fourth truth-value inconsistent, all the advantages of the three-valued approach can be retained, and that negation can be given a constructive, intuitionistic meaning that allows negative knowledge to be specified in the logic explicitly, without having to resort to extra-logical notions of stratification or to non-monotonic reasoning. The four-valued approach also allows for a computationally efficient treatment of query answering in the presence of inconsistencies. This is in contrast to the computationally intractable repair approach to inconsistency management. From a practical view-point we show that the Cylindric Star Algebra, developed by the authors, is particularly well suited for evaluating First Order queries on four-valued databases, and that the framework of data exchange can smoothly adapted to the four truth-values. |
| Databáze: | OpenAIRE |
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