Implementation of An Open and Extensible SDAI System
Huang Zhong · Chinese Journal of Computers · 2002
Standard Data Access Interface (SDAI) in STEP isolates the application program from the underlying data storage system. SDAI contains a functional definition part and several specific programming language bindings. While providing a standard way to the sharing of product data among different applications,SDAI leaves various implementation strategies to SDAI implementors. One critical issue is the implementation cost. There are various STEP application protocols,programming languages, as well as data storage systems for an implementor to choose from. Changes of any of these three aspects will lead to significant modification or even re implementation of an existing SDAI system. Dictionary based SDAI late binding will reduce the cost to implement multiple application protocols. It is the consideration of the implementor to reduce the cost increasing raised by the other two aspects. This paper describes an architecture to implement SDAI late binding on relational database systems. The architecture has a database layer to make it portable among various relational database systems,a core STEP object operation layer to provide reusable modules for different implementation languages,a data dictionary to facilitate late binding,and finally,the standard data access interface which will be called by application programs. The interfaces between these layers are identified. To store STEP data in relational database systems,we also discuss the translation of EXPRESS data models to relational data models. To distinguish between SDAI data schemas and application data schemas,we manage SDAI data schemas such as session schema in the SDAI layer,and application data schemas in the core STEP objects operations layer. We implement SDAI C late binding on Oracle based on the architecture and we will implement other SDAI language bindings on the architecture with relatively lower implementation cost.