Showing papers by "Katsumi Tanaka published in 1988"

Schema virtualization in object-oriented databases

Abstract: A description is given of the concept and implementation techniques of schema virtualization in object-oriented databases. The objective of schema virtualization is to provide users with multiple views of a database. First, the notions of virtual classes and virtual schemata, which are natural extension of views in relational databases, is introduced. Then, procedures to convert a schema into a virtual one, as well as rules schemata and their conversion should satisfy, are discussed. The key issue of the design of virtual classes and virtual schemata is 'regarding procedures as objects'. Closure properties of classes and schemata are also discussed. Finally, several implementation techniques for realizing schema virtualization in Smalltalk-80 are presented. >

Towards Abstracting Complex Database Objects: Generalization, Reduction and Unification of Set-type Objects (Extended Abstract)

Abstract: Representing and manipulating complex (database) objects are important issues in the semantic database models and object-oriented database models, most of which have a rich expressive power for complex objects In this paper, we will focus on the manipulation of complex objects, and introduce the notions and the operations for abstracting complex objects We introduce the notion of "element-based" generalization relationships between complex objects, and two new abstraction operators: reduction and unification Their algebraic properties are then formally investigated especially for "set-type" complex objects

Towards abstracting complex database objects: generalization, reduction, and unification of set-type objects

Abstract: Representing and manipulating complex (database) objects are important issues in the semantic database models and object-oriented database models, most of which have a rich expressive power for complex objects. In this paper, we will focus on the manipulation of complex objects, and introduce the notions and the operations for abstracting complex objects. We introduce the notion of “element-based” generalization relationships between complex objects, and two new abstraction operators: reduction and unification. Their algebraic properties are then formally investigated especially for “set-type” complex objects.