Semantic Generalization in a Graph-Based Data Model

This paper proposes the semantic generalization. This generalization makes it possible for a shape graph, which corresponds to a relation schema in the relational data model, to have elements by considering the semantics of the elements of the original shape graphs even if there is no common element in the original shape graphs. For this purpose, viewpoints and relationship trees are introduced. A viewpoint is a sub graph of a schema graph, and plays a role of a kind of hierarchy of concepts. A relationship tree is a hierarchy of relationships. The semantic generalization is informally and formally described. It is shown that the conventional generalization could be realized by using the semantic generalization.