Edbms Model, Access, Efficiency, And The Language And Its Application

This thesis discusses several research results on engineering database management systems (EDBMS), which mainly includes a data model, the access efficiency, an engineering data language and implementation of EDBMS/3 used for the architecture CAD.A semantic hypergraph model based on relation/network is presented. Using object-oriented method to unify descriptions for both objects and tuples, the model presents semantic links among objects, some operations on links and the method mechanism imposed on objects. In the level of the semantic hypergraph, the model can describe and operate the objects belonging to different semantic classes; while in the level of semantic graph, the model describes and operates many to many relations of the objects for each class. Therefore, in engineering application fields, the model can describe and process complex relations for multimedia objects under the management and control of EDBMS.In the method of multi-table and multi-record for main memory management, the thesis introduces the means to allow users to define the space of the working area and tables in main memory. The system will allocate the maximum space and the number of tables, if users abandon the definition. The method presents one-time-processing technique for the record block including multi-record, that means the system takes the block as a unit to process and interchange data between main memory and disk. Moreover, according to the different characteristics between sequential and random operations, the method proposes elimination and no-elimination strategies for sequential and random operations respectively. Facts have proved that this method can reduce the time of tables swapping, records swapping and unnecessary computations and examinations, increase the access efficiency of sequential and random operations. Compared with the method of the single-table and single-record, the average access efficiency is increased by 1.2 times.According to the application requirements of the architecture CAD, A novel engineering data language ( EDL/3) is presented . The fuctionalities of the language include general and special purpose. The former supports some operations for multi-base, multi-table, links among records as well as computations and statistics in databases; the latter supplies special operations used for the architecture CAD, including operations for the attributes of the variable at-...