TEMPORAL SPECIALIZATION AND GENERALIZATION

被引:31
作者
JENSEN, CS [1 ]
SNODGRASS, R [1 ]
机构
[1] UNIV ARIZONA,DEPT COMP SCI,TUCSON,AZ 85721
基金
美国国家科学基金会;
关键词
QUERY PROCESSING; SPECIALIZED TEMPORAL RELATIONS; GENERALIZED TEMPORAL RELATIONS; TAXONOMY; TIME ATTRIBUTES; TEMPORAL DATABASE; TEMPORAL SEMANTICS; TRANSACTION TIME; VALID TIME;
D O I
10.1109/69.334885
中图分类号
TP18 [人工智能理论];
学科分类号
081104 ; 0812 ; 0835 ; 1405 ;
摘要
A standard relation has two dimensions: attributes and tuples. A temporal relation contains two additional orthogonal time dimensions, namely, valid time and transaction time. Valid time records when facts are true in the modeled reality, and transaction time records when facts are stored in the temporal relation. Although, in general, 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 more or less restricted interrelationships that define several types of specialized temporal relations. The paper examines five different areas where a variety of types of specialized temporal relations are present. In application systems with multiple, interconnected temporal relations, multiple time dimensions may be associated with facts as they pow from one temporal relation to another. For example, a fact may have an associated transaction time indicating when it was stored in a previous temporal relation. 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 researchers as well as database and system designers to precisely characterize, compare, and thus better understand 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.
引用
收藏
页码:954 / 974
页数:21
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