Showing papers by "Ramez Elmasri published in 1987"
01 Feb 1987
TL;DR: A graphical representation of the ECR model and its application as the basis for an interactive query language are discussed and a method of implementing the graphical ECR interface for accessing relational database systems is proposed.
Abstract: The Entity-Category-Relationship (ECR) model extends the Entity-Relationship (ER) model with the concepts of subclass and generalization categories. In this paper a graphical representation of the ECR model and its application as the basis for an interactive query language are discussed. The proposed query language is based on algebraic operators that can be used to transform an ECR diagram so that it represents a desired query. Semantics of the algebraic operators are formally defined. A method of implementing the graphical ECR interface for accessing relational database systems is proposed.
16 citations
03 Feb 1987
TL;DR: The types of fragmentation and the criteria they should follow is provided along with how global queries in a high-level language, GORDAS, are decomposed into local queries on the fragments in a semantic data model (ECR data model).
Abstract: Fragmentation and query decomposition are considered important issues in a distributed database environment For a semantic data model (ECR data model), the types of fragmentation and the criteria they should follow is provided along with how global queries in a high-level language, GORDAS, are decomposed into local queries on the fragments This technique may be used in a heterogeneous distributed database, where the global schema presented to the user is in the high-level ECR model
6 citations