A formal definition, query language and relational database mapping for the semantic database model
Nabeil Ismaeil Al-Madani · Medical Entomology and Zoology · 1995
Conventional database models, particularly the relational model, provided data independence by separating the conceptual representation of data from the physical implementation. However, these models lack the constructs and mechanisms for modeling the complex interrelationships among data items in a real-world application environment. Semantic database models have been developed to provide a richer set of data structuring constructs and mechanisms. The Semantic Database Model (SDM) is one of the most comprehensive published semantic database models. It incorporates a wide range of constructs for expressing data abstractions, relationships among data items, and data derivation mechanisms. The SDM, however, is defined by means of examples and does not have a formally defined semantics or query language. The primary focus of this dissertation is: (1) to formally define the SDM, (2) to develop a query language for the SDM, (3) to develop a scheme that maps the structures of the SDM to relational structures, and (4) to design and develop a prototype system that implements the SDM as a front-end to a relational DBMS. The formal definition of the SDM uses a graph-based formalism for defining the structural components, and first order predicate calculus for specifying the integrity constraints of the model. The SDM query language is an English-like query language that provides commands for schema definition and modification, data retrieval and manipulation, and data update and modification. The mapping scheme provides the necessary theoretical foundations for developing the SDM Schema Management System (SDM/SMS) prototype. The SDM/SMS implements the SDM on top of a relational DBMS. It allows the user to define and manipulate schemata, browse and navigate inside schemata, and specify queries through an intuitive yet powerful graphical user interface.