An Equivalent Schema Evolution Policy Based on Path-Independence Language
基于路径无关语言的等价模式演化策略

The schema in object-oriented database (OODB) often experiences considerable changes during the development for typical application areas. After the update, the existing application programs based on the formerly schema have to be modified or rewritten, which makes a great deal of application programs obsolete. This paper addresses the problem by providing equivalent schema evolution (ESE) mechanism based on path independence (PI) program. Path-Independence program is employed as OODB's specification formalism for enhancing the adaptability of database program against the schema evolution. Equivalent schema evolution can make the existing path-independence language reuse without any modification after the schema has been updated. In addition, a solution approach of remaining the equivalent schema evolution mechanism is described in this paper as a effective working system, which as its essential feature the system to support virtual relation mechanism and object-evolving technology.