Study On The Covering Problem For Functional Dependency With Totally Ordered Temporal Scheme

The ever-increasing of database related to time makes designing temporal database very important.Because all the volume of temporal type which related to many applications in the real-world can satisfy totally ordered relationship, and totally ordered temporal scheme with the volume of totally ordered temporal type has good properties, so this article will do further study on logical design problem of temporal database in totally ordered environment, in order to provide more effective tools and methods for designing the totally ordered temporal database, which is significant for improving the performance of system.This paper mainly studies problems of the set of temporal dependency and covering in totally ordered temporal scheme.In order to comprehend the totally ordered temporal database systematically, first, the article gives comprehensive account of temporal database, imports concepts of functional dependency and totally ordered scheme module and so on in totally ordered scheme, presents derivation rules of functional dependency in totally ordered environment. It is necessary to standardize database to improve the system performance of totally ordered temporal database, but, when we break up a mode into the temporal third normal form (T3NF), it can not banish some main properties portioning or transferring function depend on the temporal candidate keywords, and when this mode is decompounded into corresponding subschemas of the temporal Boyce-Codd normal form (TBCNF), it couldn't keep functional dependency and non-destructive connectivity, and therefore this paper definit totally ordered temporal elementary keyword normal form (TO_TEKNF), in accordance with the relevant theorem and lemma we get the algorithm of TO_TEKNF, and proves the properties of terminative, retain-dependency and non-destructivity.It is indispensable for designing effective scheme decompound algorithm to solve the covering problem, base on relevant definitions and derivate rules this paper put forwards some basic concepts such as effective closure of totally ordered functional dependency sets, and presents the closure algorithm and the covering algorithm in totally ordered schme, proves correctness and validity of algorithms, and figures out the time complexity degrees.The indroduction of time dimension makes information stored in database become very huge, and redundant information increases simultaneously, how to decrease redundance of functional dependency becomes very important, so does the totally ordered temporal database. Based on this, this article discusses the covering problem of totally ordered temporal functional dependent sets at last, introduces the relevant definitions of covering in totally ordered environment, advances totally ordered non-redundancy algorithm, norms covering algoritm and minimum covering algorithm, and further standardizes totally ordered temporal database.