The Research Of Multiple Granularities In Temporal Database

In the temporal database, temporal granularity is the unit for measuring the temporal data. Ususlly we use time type to express temporal granularity. But the user may define time granularities in their wills. Temporal database should support the user to manipulate data in any time unit. But in the several implementations of temporal database, it is the user application rather than the TDBMS implements the time management. This paper discusses the way in which the temporal database manages these temporal granularities, converts between different temporal granularity representations of information and makes the conversion transparent to users. In the only realization of several TDBMSs, the meaning and explanation of granularity are all realized by user's application program now, but not TDBMS one is understood. How TDBMS manages the temporal granularities, how to change on the basis of the information that the granularity stores of different granularities, that is a main respect that studies of this article to make this kind of conversion totally transparent to database users. In addition, introduce time information in the traditional database, will cause the appearances of a series of questions, such as major key, index, consulting integrality, etc. In order to solve these problems, this article carry on systematic research on the basis of standardized theory of relation database to have many temporal database standardized theory with multi-granularities restrain. The research of the temporal granularity questions mostly concentrate on expressing the temporal granularity with the time type at present, in practical application, the expression method have heavy limitation to user self-defining granularity. This article has put forward the concept of the temporal granularity relation on the basis of five kinds of relations between the temporal granularities and collected and provided and worn out the algorithm that the old granularity defines the new granularity on the basis of the granularity relation. The paper summarizes constant,time slot,time interval; Provide the indirect temporal granularity transition on the basis of the direct temporal granularity changes algorithm. Offer the effective way for the user's self-defining granularity in practical application on the basis of temporal granularity relationship. It can be used for supporting TDBMS characteristic with multi-temporal granularity. Through this algorithm, data with all kinds of temporal granularities can be sended to user interface and realize the time management in an all-round way. In the research field of temporal database, the issue on temporal function dependency with multi-granularity has been in a deep degree and the research on the logic design of temporal database with multi-granularities has been discussed systematically. But the existing algorithm is very difficult to use in the real design of database, this is mainly because of the reason of two respects: On one hand, because time types have lean towards preface characteristic which makes operation between time type unable to realize; On the other hand, the algorithm is judged by the foundation with normal form, but so far there is no effective algorithm to judge normal form. In order to overcome above-mentioned problems, this paper presents the concepts of TEKNF and TSNF and provides an algorithm on those temporal models and proves the revelent theorem.