| Temporal information exists in every corner of our life. Computer technology is always leading the development of science and technology, therefore the applications on the combination of temporal information with database technology are needed more and more widely. Just at this moment arises temporal database. In the relational database theory, relational scheme decomposition is an effective way to eliminate redundant data and storage anomaly. In designing temporal database, decomposition of temporal module scheme is also worth our researching in depth. Actually the totally-ordered relation exists among the most of time granularities encountered in application. It is also this totally-ordered relation that makes the totally-ordered temporal type take on some important characteristics, therefore this paper mainly studies the problems of scheme decomposition of totally-ordered temporal database.In order to more effectively research the problem of scheme decomposition of temporal database for further standardization, this paper firstly investigates totally-ordered temporal candidate keywords and summarizes the attributes of the totally-ordered temporal left, right department and double department. All the totally-ordered candidate keywords can be obtained through the combination with the relational database theory and the introduction of replacement algorithm and temporal attributes related table method. And the relevant theorems and deductions will be demonstrated.It cannot eliminate some temporal data redundancy just by decomposing a totally-ordered temporal scheme into totally-ordered temporal third normal form. Only the totally-ordered and lossless connectivity can be maintained when a totally-ordered temporal scheme is decomposed into totally-ordered temporal BC normal form. It is difficult to accomplish the preservation of functional dependencies in this condition. So it is necessary for us to find a new normal form to alleviate these problems. To achieve this goal, this paper puts forward such concepts as totally-ordered elementary functional dependent, totally-ordered elementary candidate keys, totally-ordered temporal elementary key normal form concepts, using the characteristics of totally-ordered minimal cover sets present the decomposition algorithm of totally-ordered temporal elementary key normal form scheme, and discusses and analyzes the related theorem and deductions.The study of the theories and algorithms as above will effectively solve the problem of normalizing totally-ordered temporal scheme to totally-ordered temporal elementary key normal form, and pave the way for temporal database logical design. |
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