A CASE STUDY EXAMINATION DATA MODELLING IN PRACTICE Paul Groves A report submitted in partial fulfilment of the requirements of the degree of Master of Commerce (Honours) to the University of New South Wales 1988 CERTIFICATION "I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of a University or any other institute of higher learning, except where due acknowledgement is made in the text." ABSTRACT Data modelling for analysis and data base design is increasingly being viewed as a critical phase in the systems development process. This report is a comparative analysis of data modelling theory and practice. It investigates the nature of data and examines several data modelling methododologies. Current international standards for the conceptual data model are reviewed and based on this a reference framework is defined. This framework is used to compare four contemporary data modelling theories. Field testing of three of the methods is conducted, two case studies from a commercial environment and one from an academic setting. The case studies are conducted on a descriptive research basis. Results from the case studies confirm that data modelling represents a technique of growing impor­ tance in the systems development process. Increasing resources applied to the practice of relational database should ensure ensure ongoing theoretical interest and development. Although in the for­ mative stages of implementation and use, binary data modelling was seen to have achieved notable sucess in enhancing communication between project participants and in increasing user participation. As a consequence it was anticipated that system quality would improve. Limitations on the practical application of binary modelling were noted based on case study results. Several (future) empirical studies are detailed in which the quantitative and qualitative impacts of binary data modelling usage might be evaluated. 1 CONTENTS Chapter 1 INTRODUCTION . 1-1 Chapter 2 REFERENCE FRAMEWORK . 2-1 Chapter 3 DATA AND THE NATURE OF REALITY. 3-1 Chapter 4 DATA MODELS AND DESIGN . 4-1 4.1 Conventional Data Models . 4-2 4.2 Semantic Modelling v Semantic Data Models . 4-4 Chapter 5 DATABASE ARCHITECTURE................................. 5-1 5.1 Conceptual Schema - Defined... 5-1 5.1.1 Conceptual schema and the Information System . 5-3 5.1.2 Content of the conceptual schema . 5-4 5.1.3 Functions of the Conceptual Schema..... 5-5 Chapter 6 DATA MODELLING . 6-1 Chapter 7 INFORMATION SYSTEMS LIFECYCLf . 7-1 Chapter 8 DATA MODELLING METHODS: FEATURE ANALYSIS.......... 8-1 8.1 Entity Relationship Modelling . 8-2 8.1.1 Concepts . 8-2 8.2 Fact Based Data Analysis and Design . 8-5 8.2.1 Design Process. 8-5 8.3 Nijssen' s Information Analysis . 8-8 8.3.1 Concepts . 8-9 8.3.2 NIAM Development Lifecycle . 8-10 8.3.3 Information Base: NIAM Sentence Model . 8-11 8.3.4 Semantics . 8-12 8.4 Active and Passive Component Modelling (ACM/PCM) . 8-13 8.4.1 Abstraction Modelling . 8-13 8.4.2 Structural Modelling . 8-14 8.4.3 Behavioural Modelling . 8-16 8.4.4 ACM/PCM Design Modelling . 8-17 iii Chapter 9 DATA MODELLING METHODS: COMPARATIVE REVIEW . 9-1 9.1 Lifecycle Support . 9-2 9 .1.1 Representation and Communicability . 9-4 9 .1.2 Abstraction Support . 9-7 9.1.3 Documentation Support..... 9-10 9.1.4 User Orientation . 9-12 9.1.5 Semantic Expressiveness . 9-14 9.1.6 Quality Control . 9-16 9.1.7 Comparative Review - Summary . .. 9-18 Chapter 10 UNIVERSITY OF NEW SOUTH WALES ....................... 10-1 10.1 Objectives . 10-1 10.2 Research Method . 10-1 10.3 Environment . 10-2 10.4 Database Systems Development . 10-4 10.4.1 Database Systems - 1984 . 10-5 10.4.2 Database Systems - 1985 . 10-7 10.4.3 Database Systems - 1986 ........................................... 10-10 10.5 Interview Plan ...................................................... 10-12 10.5.1 Lecturers ....................................................... 10-12 10.5.2 Tutors .......................................................... 10-15 10.5.3 Students ........................................................ 10-16 10.6 Conclusion ........................................................ 10-17 Chapter 11 AUSTRALIAN MUTUAL PROVIDENT. .11-1 11.1 Objectives . 11-1 11.2 Research Method . 11-2 11.3 Environment . 11-3 11.3.1 Hardware.... 11-3 11.3.2 Software History . 11-4 11.3.3 Software Current . 11-5 11.4 Data Modelling . 11-6 11.5 Systems Lifecycle . 11-8 11.6 Data Modelling Experiences . 11-9 11.6.1 User experiences ................................................. 11-11 11.7 Conclusion ........................................................ 11-12 iv Chapter 12 DIGITAL EQUIPMENT CORPORATION ...................... 12-1 12.1 Introduction. 12-1 12.2 Corporate Environment . 12-2 12.3 Local Environment . 12-3 12.4 Methodolgy review . 12-4 12.5 Systems Analysis. 12-5 12.6 Modelling and Partitioning . 12-6 12.6.1 Conceptual Modelling . 12-8 12.6.2 Functional modelling . 12-9 12.6.3 Physical modelling ................................................ 12-10 12.7 An inventory application .............................................. 12-10 12.8 Modelling experiences ................................................ 12-12 12.9 Conclusion ........................................................ 12-15 Chapter 13 SUMMARY . 13-1. 13.1 Case study conclusions . 13-2 13.2 Research Limitations . 13-4 13.3 Future Research. 13-5 Appendix A SUBJECT DESCRIPTIONS . A-1. FIGURES 1 ACM/PCM Design Phases . 8-17 2 Candidate keys . ..