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Temporal Specialization and Generalization
December 1994 (vol. 6 no. 6)
pp. 954-974

A standard relation has two dimensions: attributes and tuples. A temporal relation contains two additional orthogonal time dimensions: valid time records when facts are true in the modeled reality, and transaction time records when facts are stored in the temporal relation. Although there are no restrictions between the valid time and transaction time associated with each fact, in many practical applications the valid and transaction times exhibit restricted interrelationships that define several types of specialized temporal relations. This paper examines areas where different specialized temporal relations are present. In application systems with multiple, interconnected temporal relations, multiple time dimensions may be associated with facts as they flow from one temporal relation to another. The paper investigates several aspects of the resulting generalized temporal relations, including the ability to query a predecessor relation from a successor relation. The presented framework for generalization and specialization allows one to precisely characterize and compare temporal relations and the application systems in which they are embedded. The framework's comprehensiveness and its use in understanding temporal relations are demonstrated by placing previously proposed temporal data models within the framework. The practical relevance of the defined specializations and generalizations is illustrated by sample realistic applications in which they occur. The additional semantics of specialized relations are especially useful for improving the performance of query processing.

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Index Terms:
temporal databases; query processing; generalisation (artificial intelligence); data structures; transaction processing; database theory; temporal specialization; temporal generalization; specialized temporal relations; time attributes; tuples; valid time; transaction time; restricted interrelationships; interconnected temporal relations; multiple time dimensions; generalized temporal relations; predecessor relation querying; successor relation; temporal data models; semantics; query processing performance; taxonomy; temporal database; temporal semantics
C.S. Jensen, R. Snodgrass, "Temporal Specialization and Generalization," IEEE Transactions on Knowledge and Data Engineering, vol. 6, no. 6, pp. 954-974, Dec. 1994, doi:10.1109/69.334885
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