基于带根连通有向图的对象集成模型及代数

A Data Model and Algebra for Object Integration Based on a Rooted Connected Directed Graph

提出一种便于异构数据源集成的公共数据模型——ＯＩＭ对象模型．它基于带根连通有向图，图中可出现环路，因而能自然地描述复杂对象与其成员对象间的引用关系和ＷＷＷ上ＨＴＭＬ文件间的链接关系．它的每个对象含有描述符，特别适合于描述那些没有显式模式或模式无法预知的数据对象．ＯＩＭ对象代数提供对象并、差、选择、投影、粘贴及切削６种操作．比关系代数具有更大的灵活性。

A data model named OIM is proposed in this paper as the common data model for integration of heterogeneous data sources. Based on rooted connected directed graph both cyclic and acyclic, OIM can describe the relationship of a complex object and its component objects, as well as the links between HTML files in World Wide Web naturally. As the metadata is associated with each object, OIM is especially suitable for describing objects without explicit predictable data schemata. As the formal foundation for query decomposition and optimization, a new algebra called OIM algebra, which includes six operations, i.e., object union, difference, select, project, paste and cut, is proposed. In comparison with relational algebra, OIM algebra is more flexible and powerful.