Information Systems Engineering An Introduction

This book presents a selection of subjects which the authors deem to be important for information systems engineers. The book is intended for introductory teaching. We have tried to write the book in such a way that students with only fragmented knowledge of computers are able to read the book without too many difficulties. Students who have had only an intro­ ductory course in computer programming should be able to read most of the book. We have tried to achieve simplicity without compromising on depth in our discussions of the various aspects of information systems engineering. So it is our hope that also those who have deeper knowledge in computing may find pleasure in reading parts of the book. The writing of a textbook is a major undertaking for its authors. One is quite often forced to reexamine truisms in the subject area, and must be prepared to reevaluate one's opinions and priorities as one learns more. In particular this is so in new fields, where formalisms have been scarcely used, and where consensus has not yet emerged either on what constitutes the subject area or on how practical problems within the field shall be approached. Contemporary practice in computer applications is confronted with an increasingly complex world, both in a technical sense and in the complexity of problems that are solved by computer.

1. Introduction.- 1.1 Two Information System Examples.- 1.1.1 The IFIP Conference Example.- 1.1.2 A University Administration System.- 1.2 Information Systems Modeling.- 1.2.1 Conceptual Models Have a Key Role in IS-Design.- 1.2.2 Four Different Modeling Approaches.- 1.2.3 Modeling Approaches May Be Classified According to Their Time Perspective.- 1.2.4 Desirable Features of a System Specification Model.- 1.3 Contemporary Changes in System Development Practices.- 1.4 System Development Activities.- 1.5 The Methods Problem in Information Systems Engineering.- 1.6 Information Systems Analysis Approaches.- 2. Structured Analysis and Design.- 2.1 Structured Analysis.- 2.1.1 The Process Aspect — Dataflow Diagrams.- 2.1.2 Defining the Processing Rules.- 2.1.3 The Data Aspect — Flows and Stores.- 2.1.4 Resolution of Data Access Conflicts.- 2.2 Structured Design.- 2.2.1 Software Structure Specification.- 2.2.2 The System’s Architecture.- 2.2.3 Refining the Subprogram Design.- 2.2.4 Packaging of Subprograms into Implementation Units.- 2.3 User Interfaces.- 2.3.1 The User and the Usage ofInteractive Systems.- 2.3.2 Interaction Styles and Techniques.- Exercises.- 3. Software Design.- 3.1 A Review of Software Terminology.- 3.1.1 A Standard Software Terminology is Lacking.- 3.1.2 Software Component Independence.- 3.1.3 Code-Level Concepts.- 3.2 Software Design for Maintainability.- 3.2.1 Subprogram Cohesion.- 3.2.2 Subprogram Coupling.- 3.2.3 Subprogram Structures.- 3.3 Program Structures for Hierarchical Files.- 3.3.1 Jackson’s Structured Programming (JSP).- 3.3.2 Structured Design for Hierarchical Files.- 3.4 The Object Oriented Approach.- 3.4.1 Object Orientation and Structured Analysisl/Design.- 3.4.2 Properties of Software Objects.- 3.4.3 Object Oriented Analysis and Design.- 3.5 Principles for Creating Software with Acceptable Response Times.- 3.6 Workload Analysis of Software Design Specifications.- 3.6.1 An Example of Transactions on Data Stores.- 3.6.2 Estimation of Traffic Load.- 3.6.3 Estimation of Penalties Because of One Transaction Activation.- 3.6.4 Estimation of Penalties for Systems of Many Transaction Types.- 3.6.5 An Example of Traffic Load Analysis.- 3.6.6 On the Estimation of the Design Parameters.- 3.6.7 An Example of Sensitivity Analysis.- Exercises.- 4. Database Design.- 4.1 Files and Databases.- 4.1.1 File Organization Techniques.- 4.1.2 Database Management Systems.- 4.1.3 Data Security.- 4.2 Data Model Alternatives.- 4.2.1 The Hierarchical Data Model.- 4.2.2 The Network Model.- 4.2.3 The Relational Data Model.- 4.2.4 The Entity-Relationship Model.- 4.3 Issues in Database Physical Design.- 4.3.1 Properties of Database Management Systems.- 4.3.2 Translation and Analysis of the Logical Design.- 4.3.3 Physical Design Approaches.- 4.4 Database Design Constrained by Traffic Load Estimates.- 4.4.1 The Example.- 4.4.2 Traffic Load Estimation.- 4.4.3 Reasoning About the Consequences of the Transaction Traffic.- 4.4.4 Refining the Database Design.- 4.4.5 Interpretation of the T-matrix.- Exercises.- 5. Rule Modeling.- 5.1 Rule Formulation.- 5.1.1 Rule Processing Versus Rule Manipulation.- 5.1.2 Ambiguity in Range Specification.- 5.1.3 Ambiguity in and/or Combinations.- 5.2 Simple Rule Modeling Tools.- 5.3 Decision Trees.- 5.3.1 Standard Decision Tree Development.- 5.3.2 Progressive Decision Tree Development.- 5.3.3 Completeness Checking of Decision Trees.- 5.3.4 Syntactical Simplification.- 5.3.5 Syntactical Simplification Process.- 5.3.6 Semantical Simplification.- 5.4 Decision Tables.- 5.4.1 Standard Decision Table Construction.- 5.4.2 Extended-Entry Decision Tables.- 5.4.3 Indifference and Consolidation.- 5.4.4 Completeness of Decision Tables.- 5.4.5 Semantical Simplification of Decision Tables.- 5.5 Structured English.- 5.6 Comparison of Decision Trees, Decision Tables and Structured English.- 5.7 Process Logic and Expert Systems.- 5.8 An Introduction to Logical Inference.- 5.8.1 Rewriting of Logical Formulas.- 5.8.2 The Resolution Principle.- 5.8.3 Three Main Tasks for Applying Logical Proof.- 5.8.4 Some Properties of Proof Methods.- Exercises.- 6. Information Systems Evolution: The Software Aspect.- 6.1 The Role of Standard Software in Information Systems Evolution.- 6.1.1 Common, Standard, and Custom-Tailored Software.- 6.1.2 Application Platforms, Common Software, and Information Systems Integration.- 6.1.3 The Architecture of Common Systems.- 6.2 The Installation of Software Systems in Organizations.- 6.2.1 Installation Approaches.- 6.2.2 Who is the User?.- 6.2.3 Installation Experiences.- 6.2.4 Features of an Installation Strategy.- 6.3 Evolutionary Behavior of Large Software Systems.- 6.3.1 An Analysis of Observed Evolutionary Behavior.- 6.3.2 Basic Assumptions of Different Models of Evolutionary Behavior.- 6.3.3 The Impact of Error Propagation on Structural Degeneration.- 6.3.4 The Impact of Resource Allocation on Structural Degeneration.- Exercises.- 7. Managing Information Systems Development Projects.- 7.1 Project Selection: The Master Plan.- 7.2 The Project Life Cycle.- 7.2.1 Phase 1: Pre-project Study.- 7.2.2 Phase 2: Requirement Specification.- 7.2.3 Phase 3: System Modeling and Evaluation.- 7.2.4 Phase 4: Functional Specification.- 7.2.5 Phase 5: Data Processing System Architecture.- 7.2.6 Phase 6: Programming.- 7.2.7 Phase 7: System Installation.- 7.2.8 Phase 8: Project Evaluation.- 7.3 Project Evaluation and Control.- 7.4 The Information System Development Organization.- 7.4.1 The Information System Department.- 7.4.2 The Functional “Large-Project” Structure.- 7.4.3 The Project Team Structure.- Exercises.- 8. Information System Support for Information System Development.- 8.1 Contemporary Environments for Supporting System Development.- 8.2 The Functional Properties of Support Systems for Information Systems Engineering (lSE-systems).- 8.3 A Database for Supporting Information Systems Engineering.- 8.4 Information Systems Configuration Management.- 8.4.1 Versions, Revisions and Variants.- 8.4.2 Change Management.- 8.4.3 Efficient Storage of Components.- 8.4.4 Software Manufacture.- Exercises.- 9. Engineering Design Principles for Unsurveyable Systems.- 9.1 The Engineering Design Process.- 9.1.1 Problem Formulation.- 9.1.2 Problem Analysis.- 9.1.3 Solution Generation.- 9.1.4 Solution Selection.- 9.1.5 Design Specification.- 9.1.6 Implementation.- 9.1.7 Modification.- 9.1.8 The Engineering Design Process: Ideals and Reality.- 9.2 Properties of Unsurveyable Systems.- 9.2.1 Problems of the Whole and Problems of Components.- 9.2.2 The System Concept.- 9.2.3 Dealing with Unsurveyable Systems.- 9.2.4 Langefors’ Fundamental Principle for System Development Work.- 9.2.5 A Guideline for System Development Work.- 9.2.6 The Feasibility Study.- 9.3 Development of Non-constructive Systems.- 9.3.1 Properties of Wicked Problems and Tame Problems Contrasted.- 9.3.2 Principles for the Solution of Wicked Problems.- Exercises.- 10. Information and Information Systems.- 10.1 Relationships Between Knowledge and Information.- 10.1.1 Types of Knowledge.- 10.1.2 Knowledge, Information, and Information Processes.- 10.1.3 Some Important Properties of Information.- 10.2 Ways of Obtaining Knowledge.- 10.3 Formal and Informal Information.- 10.4 The Information System and Its Environment.- 10.5 Information Systems Viewed as Production Organizations.- 10.6 Self-Referential Information Systems.- 10.6.1 Static Programs.- 10.6.2 Problem Oriented Programs.- 10.6.3 Evolutionary Programs.- Exercises.- 11. Three Domains of Information Systems Modeling — and the Object-Oriented Approach.- 11.1 Subject Domain Modeling.- 11.2 Interaction Domain Modeling.- 11.3 Implementation Domain Modeling.- 11.4 The Basic Concepts of the Object-Oriented Approach.- 11.4.1 Objects.- 11.4.2 Object Class.- 11.4.3 Encapsulation.- 11.4.4 Inheritance.- 11.4.5 Polymorphism.- 11.5 Object-Oriented Analysis.- 11.5.1 Coad and Yourdon’s Approach.- 11.5.2 The Object Modeling Technique..- 11.6 Ob