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4 lation and optimization. These are essential constituents of the iterative process, leading to a feasible and, one hopes, optimal design. 1.3 Content of the Book In Chapter 2 we present briefly the history of CAD. The main components of CAD systems are identified, and their principal functions described. Economi­ cal and interdisciplinary aspects are discussed. Chapter 3 starts with a systems analysis of the design process. The notion of a process is introduced as a fundamental tool to describe activities like design as a whole, computer-aided design, program executions, terminal sessions etc. The environment and the resources which the environment must supply for the successful execution of any process are discussed. The problem of modelling the design objects in an abstract schema and the interrelation between the schema and the planning of the individual step in the design are analysed. Chapter 4 concentrates on the interfaces among the components of a CAD system, including the human operator. The problem of mapping an abstract schema onto the capabilities of various programming, command, or data de­ scription languages is described in detail. Emphasis is laid upon the resource aspect and its influence on the design of CAD systems. The concept of a CAD software machine is introduced, and rules for designing such machines are given.

1 Introduction.- 1.1 Purpose of This Book.- 1.2 Scope of CAD.- 1.3 Content of the Book.- 1.4 Summary.- 1.5 Acknowledgements.- 1.6 List of Frequently-Used Abbreviations.- 2 History and Basic Components of CAD.- 2.1 History.- 2.2 Modules, Functions, Components.- 2.3 Interactive Graphic Interfaces.- 2.3.1 The Graphical Kernel System.- 2.3.2 The Graphical Dialogue System.- 2.4 Data Bases for CAD.- 2.5 Economical Aspects of CAD.- 2.6 Interdisciplinary Aspects of CAD.- 2.7 Summary.- 2.8 Bibliography.- 3 The Process Aspect of CAD.- 3.1 Modelling of the Design Process.- 3.1.1 A Crude Model of the Design Process.- 3.1.2 A More Refined Model of the Design Process.- 3.1.3 Design Processes and Design Environments.- 3.1.4 Differences Between Conventional Design and CAD.- 3.1.5 A Network of the Design Process.- 3.2 CAD Processes.- 3.2.1 Design Process and CAD Process.- 3.2.2 Design Process Characteristics and Their Influence upon the CAD Process.- 3.2.3 The Environment of CAD.- 3.2.3.1 The Organization.- 3.2.3.2 The Human Environment.- 3.2.3.3 Computer Resources.- 3.2.3.4 The Interaction Phases of the CAD Process.- 3.2.4 The State of CAD Processes.- 3.2.4.1 The Lifetime of Processes.- 3.2.4.2 The Representation of the Process State.- 3.2.4.3 The Operating State.- 3.2.5 The Problem of Resources.- 3.2.5.1 Resource Availability and Conflicts of Resource Requirements.- 3.2.5.2 The Efficiency Aspect of Resources.- 3.2.5.3 CAD Machines and CAD Tools.- 3.3 Modelling in CAD.- 3.3.1 Developing a Schema.- 3.3.1.1 Basic Considerations.- 3.3.1.2 A Sample Problem.- 3.3.1.3 Naming of Objects and Attributes.- 3.3.1.4 Alternatives for a First Schema.- 3.3.2 Influence of the Operations upon Schema Planning.- 3.3.3 Subschema Transformations.- 3.3.3.1 Subschema Transformations as Part of the Schema.- 3.3.3.2 The n-square Problem of Subschema Transformations.- 3.3.4 Flexibility - A Measure of Prudence - Versus Efficiency.- 3.3.5 Schema Planning and Design Process Planning.- 3.3.5.1 Subprocess Planning and Data Validity.- 3.3.5.2 The Information Packages.- 3.3.6 Resulting Data Base Management System Requirements.- 3.4 Summary.- 3.5 Bibliography.- 4 The Architecture of CAD Systems.- 4.1 The Gross Architecture.- 4.1.1 Components.- 4.1.2 Interfaces.- 4.1.2.1 Development and Installation of a CAD System.- 4.1.2.2 The Invocation of a CAD System.- 4.1.2.3 Functional Interfaces in a CAD System.- 4.1.2.4 Man-Machine Communication Channels.- 4.1.3 CAD Tools and CAD Machines.- 4.1.3.1 Tools Used in CAD System Application.- 4.1.3.2 Tools Used in CAD System Development.- 4.2 Data Models.- 4.2.1 Mapping.- 4.2.1.1 The Ideal Situation.- 4.2.1.2 Reasons for Non-Ideal Mapping.- 4.2.1.3 Mapping Around the Language.- 4.2.1.4 Mapping Between Aspects.- 4.2.2 Binding.- 4.2.3 The Block Structure Dilemma.- 4.2.4 Algorithmic Modelling.- 4.3 The Resource Aspect.- 4.3.1 Software Machine Design.- 4.3.2 Designing Against Resource Conflicts.- 4.3.2.1 The Abstract Machine.- 4.3.2.2 Process State Representation.- 4.3.2.3 The Concrete Machine.- 4.3.2.4 Resource Management Strategies.- 4.3.2.5 The Components of a Software Machine.- 4.3.3 A Sample Software Machine: The Stack Machine.- 4.3.3.1 The Task and a Simple Solution.- 4.3.3.2 Planning of the Stack Machine.- 4.3.3.3 Implementation of the Stack Machine.- 4.3.4 Distributed Systems.- 4.3.5 The Graphical Kernel System GKS as a Software Machine.- 4.3.5.1 The Process Aspect in GKS.- 4.3.5.2 The Resource Aspect in GKS.- 4.4 Summary.- 4.5 Bibliography.- 5 Implementation Methodology.- 5.1 Techniques and Tools for CAD System Development.- 5.2 Computer Graphics.- 5.2.1 Introduction.- 5.2.2 Interactive Graphics Systems.- 5.2.3 Graphical I/O Devices.- 5.2.3.1 Input Devices.- 5.2.3.2 Output Devices.- 5.2.3.3 CAD Workstations.- 5.2.4 The Graphical Kernel System (GKS).- 5.2.4.1 System Description.- 5.2.4.2 GKS Examples.- 5.3 CAD System Use of Interactive Graphics Functions.- 5.3.1 The KI System.- 5.3.2 The GRAD AS System.- 5.4 Design of Efficient CAD Data Bases.- 5.4.1 Introduction.- 5.4.2 CORAS ― Core System for Associative Storage.- 5.4.3 A CORAS Extension for CAD Applications.- 5.4.4 CSDL as an Example of a Language for Designing Conceptual Schemata of Data Bases.- 5.5 Integrated Systems and Methods Bases.- 5.5.1 The Concept of Integrated Systems.- 5.5.2 REGENT as an Example of a CAD System Nucleus.- 5.5.2.1 Dynamic Program Management.- 5.5.2.2 Data Structure Management.- 5.5.2.3 File Management.- 5.5.3 Methods Bases.- 5.6 Summary.- 5.7 Bibliography.- 6 Engineering Methods of CAD.- 6.1 Geometry Handling.- 6.1.1 Introduction: Points in 3-D Space.- 6.1.2 The Hidden-Line/Hidden-Surface Problem.- 6.1.2.1 General Considerations.- 6.1.2.2 The Priority Procedure.- 6.1.2.3 The Overlay Procedure.- 6.1.2.4 Generalization of the Visibility Problem.- 6.1.3 3-D Modelling.- 6.1.3.1 Introduction.- 6.1.3.2 Wire-Frame Models.- 6.1.3.3 Surfaces in Space.- 6.1.3.4 3-D Solid Modelling.- 6.2 Numerical Methods.- 6.2.1 Introduction.- 6.2.2 Finite Element Methods.- 6.2.3 Finite Difference Methods and Other Methods.- 6.2.4 Simulation.- 6.2.4.1 Survey.- 6.2.4.2 Simulation Languages.- 6.2.5 Optimization.- 6.2.5.1 Problem Formulation.- 6.2.5.2 Optimization Problem Characteristics.- 6.2.5.3 Applications.- 6.3 Computer Graphics for Data Presentation.- 6.3.1 Introduction.- 6.3.2 Functions of One Variable.- 6.3.2.1 Diagrams.- 6.3.2.2 Representations of Several Functions in One Diagram.- 6.3.3 Functions of Two Variables.- 6.3.3.1 Marker Clouds.- 6.3.3.2 Hatching, Shading and Coloring.- 6.3.3.3 Contour Plotting.- 6.3.3.4 Pseudo-Perspective View.- 6.3.3.5 Vector Plots.- 6.3.3.6 Two-Dimensional Functions on Curved Surfaces.- 6.3.4 Functions of More than Two Variables.- 6.3.5 Graphic Editing.- 6.4 Summary.- 6.5 Bibliography.- 7 CAD Application Examples.- 7.1 Typical Classes of Applications.- 7.1.1 Numerical Analysis and Presentation.- 7.1.2 Three-Dimensional Applications.- 7.1.3 Functional and Geometrical Layout.- 7.2 CAD Application in some Specific Examples of Industry.- 7.3 Bibliography.- 8 Trends.- 8.1 Availability of Computer Power.- 8.1.1 Configuration.- 8.1.2 Hardware.- 8.1.3 Graphics Terminals.- 8.2 System Architecture and Software.- 8.2.1 Special-Purpose Systems.- 8.2.2 General Purpose Systems.- 8.2.3 Distribution of Processing Power.- 8.2.4 Languages.- 8.2.5 CAD Systems in Research and Development (R&D).- 8.2.6 Problem-Solving Methods for CAD.- 8.3 Social Aspects.- 8.3.1 Education.- 8.3.2 Ergonomic Aspects.- 8.3.3 Acceptance.- 8.4 Standardization.- 8.5 Summary.- 8.6 Bibliography.- 9 Subject Index.- 10 Author Index.- Color Plates.