The Logical Record Access Approach to Database Design

Electrical apparatus and more particularly vacuum electrical circuit breaker apparatus is taught. The electrical apparatus has a cylindrical movable terminal stem which is to be interconnected with a fixed terminal by way of a flexible conductor which is nevertheless relatively stiff and self supporting. This is accomplished by using interlayered elongated rectangular plates or sheets between the two aforementioned terminals. Connection to the circular stem is made by utilizing offset tabs around the periphery of a central hole at one end of each of the sheets. The offset allows the tabbed opening to be inserted over the stem. After which the tabs are sandwiched or compressed to lie in the plane of the sheet thus causing the edges of the tab to flow around the stem reducing contact resistance. Because there are multiple sheets in each flexible conductor packet, the number of three point contacts between the flexible conductors and the stem is increased.

An Overview of Recent Data Base Research.

Evolution of research and practice in the area of conceptual modelling for information systems during more than four decades is examined. It focuses on activities related to research and practice in the early system development phases. It comments on a large number of modelling methods published in the 1960-ies, 70-ies, and 80-ies as well as on the report “Concepts and Terminology of the Conceptual Schema and the Information Base” reporting the work by the ISO working group ISO/TC97/SC5/WG5 in the early 80-ies. Approaches which are based on a temporal and deductive view of the application domain as well as object-oriented modelling languages are acknowledged. The paper continues with a discussion of principles and research problems related to a topic we call “Enterprise Modelling” and “Ontology Modelling”. The role of conceptual modelling in information systems development during all these decades is seen as an approach for capturing fuzzy, ill-defined, informal “real-world” descriptions and user requirements, and then transforming them to formal, in some sense complete, and consistent conceptual specifications. During the last two decades an additional role of modelling has evolved - to support user and stakeholder participation in enterprise analysis and requirements formulation and in development of shared conceptualisations of specific domains.

From Information Algebra to Enterprise Modelling and Ontologies — a Historical Perspective on Modelling for Information Systems

This paper provides an integrated approach for research related to the problem of database design. The process of database design is classified into five phases: requirements analysis, view modeling, view integration, view restructuring, and schema analysis and mapping. The input, processing steps, and output for each phase are described. The problems associated with each phase are pointed out. Existing approaches to database design are reviewed and related to these five phases. The significance of this integrated approach for the development of computer-aided methodologies for database design is discussed.

An Integrated Approach to Database Design

The importance of "data abstraction" has rapidly emerged over the past few years. The massive sharing of data contemplated by database management technologists and the limitations of widely used programming languages have provided a strong stimulus to change the current technology. In the at tempt to free users and programmers from the details of conventional computer systems, work has proceeded in two directions: (1) In the language area, there have been investigations to allow more natural operations over types of data that more closely resemble real world objects. [For example, see 5, 6, 9, 12]. (2) In the database area, there have been investigations to promote more natural methods for manipulating large databases. [For example, see 1, 8, 13, 16, 20]. The purpose of the Conference on Data Abstraction was to promote and bring together these two relatively disjoint areas of research. This note is based on remarks made in the closing session of the conference. Ted Codd, Barbara Liskov, and Peter Wegner contributed to the closing session. Only those papers presented at the conference are cited here.

Two views of data abstraction

The task of physical data base design in an DBTG enviornment is examined. Generation of an internal schema which considers questions of storage versus access costs, efficient implementation of data relationships, efficient placement of data within the data base and allocation of primary and secondary storage is shown to be a formidable task.

Current data base design aids are reviewed. One aid, a sophisicated mathematical model of DBTG data bases (Gerritsen 1977) is shown to be a potentially valuable tool. A limitation of this model is that no optimization algorithm other than total enumeration has been found.

This paper proposes an implementation of the Gerritsen model. An interactive design tool, based upon the Gerritsen model, is discussed. A Data Base Design Decision Support System (DBD-DSS) for use by the DBA is developed. The objectives and structure of the DBD-DSS are examined, A comprehensive example illustrating both the user interface and the potential benefits of the interactive tool is presented.

Sam Nachmens

Papers

CS4: a tool for database design by infological simulation (abstract)

From Information Structures to DBTG Data Structures.