Schema Evolution of an Object-Oriented Real-Time Database System for Manufacturing Automation

• Authors: Lei Zhou;Elke A. Rundensteiner;Kang G. Shin
• Venue: IEEE Transactions on Knowledge and Data Engineering
• Year: 1997

The database schemata often experience considerable changes during the development and initial use phases of database systems for advanced applications such as manufacturing automation and computer-aided design. An automated schema-evolution system can significantly reduce the amount of effort and potential errors related to schema changes. Although schema evolution for nonreal-time databases was the subject of previous research, its impact on real-time database systems remains unexplored. These advanced applications typically utilize object-oriented data models to handle complex data types. However, there exists no agreed-upon real-time object-oriented data model that can be used as a foundation to define a schema-evolution framework. Therefore, we first design a conceptual real-time object-oriented data model, called Real-time Object Model with Performance Polymorphism (ROMPP). It captures the key characteristics of real-time applications驴namely, timing constraints and performance polymorphism驴by utilizing specialization-dimension and letter-class hierarchy constructs, respectively. We then re-evaluate previous (nonreal-time) schema-evolution support in the context of real-time databases. This results in modifications to the semantics of schema changes and to the needs of schema-change resolution rules and schema invariants. Furthermore, we expand the schema-change framework with new constructs驴including new schema-change operators, new resolution rules, and new invariants驴necessary for handling the real-time characteristics of ROMPP. We adopt and extend an axiomatic model to express the semantics of ROMPP schema changes. Using manufacturing-control applications, we demonstrate the applicability of ROMPP and the potential benefits of the proposed schema-evolution system.