Schema Evolution of an Object - Oriented Real - TimeDatabase System for Manufacturing

| 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 signiicantly reduce the amount of eeort and potential errors related to schema changes. Although schema evolution for non-real-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 foundation to deene a schema evolution framework. Therefore, we rst design a conceptual real-time object-oriented data model, called ROMPP (Real-time Object Model with Performance Polymorphism). It captures the key characteristics of real-time applications, namely, timing constraints and performance polymorphism, by utilizing specialization dimension and letter class hierarchy constructs , respectively. We then re-evaluate previous (non-real-time) schema evolution support in the context of real-time databases. This results in modiications 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|including new schema change operators, new resolution rules, and new invariants|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 potential beneets of the proposed schema evolution system.