Engine Engineering Database Of Key Technologies

The thesis discusses some research results on engineering database management system, which mainly includes the architecture, transaction processing, concurrency control, security of the engineering database, and implementation of a prototype of secure database system under Windows environments.In views of characteristics of engineering application, an extended Client/Server (C/S) architecture is adopted in engine engineering database system, which supports the multi-server. In the function division aspect, it makes client more powerful through allowing to place local databases and local DBMS on the client machine. It supports two kinds of data access mode: the plain transaction access and the engineering transaction access. RDA (Remote Database Access) is provided for short plain transaction processing to the simple data, CheckOut/Checkln is used for long engineering transaction processing.In the paper, an engineering transaction processing model and commit protocol is presented which is fit for CAD application. That is a nested transaction model and an improved 2PC (two phase commit) protocol. It allows user transaction processing to include some server transaction and a client transaction, which are separately responsible to access shared data and local data. When the processing involves multiple nodes, the improved 2PC protocol can ensure correct commitment of the global transaction, it allows sub-transaction abort and farther-transaction ends under not all sub-transactions have executed. In the other hands, a corresponding concurrency control algorithm is introduced to adapt to the system's access mode and to raise the concurrency degree. The algorithm is based on the lock to control the concurrent accesses.Through studying and analyzing the database security, to provide a database model and security rules which reach Bl level security standard. The Bl level security includes Discretionary Access Control(DAC) .Mandatory Access Control(MAC) and Audit . DBMS draws a series of security rules referred the Bell-Lapadula model and SeeView model and implements DAC based on role, polyinstantiation MAC and multigranularity Audit o DAC solves the problems of role inheritance. right contain, authorization identify and cascade revoke,etc; MAC includes subject and object security setup rule, security modify rule and multilevel relation access operation rule, etc; Audit allows to make the subject object or operation type as different audit object to implement flexible and multigranularity audit method o The model is designed act as a proxy to access daemon database.A secure engineering database management system is designed and implemented. At present, a demonstrated version of the model is implemented which runs on the micro computer's window NT environments.