1 Introduction Personal CASE is a Computer Aided Software Engineering program. It helps software designers and systems analysts create and organize a system design using Data Flow Diagrams and a Data Dictionary. Personal CASE is a Microsoft Windows Application which works on most IBM-Compatible Personal Computers. A Data Flow Diagram shows the relationships between the various components of a system. It tracks the movement and transformation of information as it is processed. This manual contains a tutorial on the use of Data Flow Diagraming in the system design life cycle. There are a number of accepted forms which a Data Flow Diagram may take. Personal CASE uses the commonly accepted form created by Gane & Sarson. A diagram is created from a set of standard symbols representing Process, Data Store and External Entity components. The symbols are connected by arrows, representing the flow of data. This is a Data Flow Diagram created with Personal CASE: (Illustration omitted from the text file) The Data Dictionary keeps track of descriptions of all system components. Each description is given a unique identifier by the designer. These identifiers are used to associate descriptions with actual diagram components. Both private and global data dictionaries can be used by a design. Here is an example of the information stored in the data dictionary: (Illustration omitted from text file) Personal CASE operates within the Microsoft Windows Environment on most IBM-Compatible personal computers. Personal CASE uses all of Windows’ data presentation and interaction abilities in a powerful and straightforward fashion. You don’t need to be an artist or graphics professional to quickly create presentation quality diagrams. Personal CASE combines the best tools from desktop publishing, graphics, word processing, hypertext and CAD programs into a form especially made for software designers and systems analysts. Personal CASE keeps up with your thinking during the design process and helps you organize the results. What is Included with Personal CASE Personal CASE is distributed on a single 360k 5 1/4" or a single 720k 3 1/2" diskette. The package contains both diskettes. Use the appropriate diskette for your computer.The distribution diskette contains both the program and a set of 2 Introduction sample designs created with Personal CASE. An abridged manual is included with the demo version of the program. It includes the quick reference section which briefly describes the operation of the entire program. Hardware Requirements Personal CASE is a Microsoft Windows Application. It will run on any hardware configuration supported by the Windows operating environment. The range of hardware supported by Personal CASE is limited only by the compatibility of that hardware with Microsoft Windows. This includes all models of the IBM Personal Computer, all models of the IBM Personal System/2, all Compaq computers and most other compatible systems. Software Requirements MS-DOS (or PC-DOS) Version 3.1 or later must be used. Microsoft Windows 286 or Windows 386 version 2.1 or later is required. This software is not included with Personal CASE and must be purchased separately. See your Microsoft dealer for details. We assume that you are familiar with the operation of Windows itself, using either a mouse or the keyboard. If not, then first review the Windows User’s Guide that accompanies Windows. If you plan to use Personal CASE in a networked environment, the network hardware and operating system must support DOS 3.1 file and record locking. Most popular vendors provide this support. Installation To install Personal CASE, copy the contents of the distribution diskette onto your fixed disk using either the DOS COPY command, or the Windows MS-DOS Executive. The diskette contains the program file, documentation and sample design files. 3 2. Data Flow Diagrams This chapter briefly describes how data flow diagrams are used in the systems design process and how Personal CASE manages data flow diagrams. In this chapter: - Basic Principles - A Typical Model - Components - Multi-page Diagrams - Related Reports Produced by Personal CASE For a more detailed data flow diagram tutorial, refer to textbooks such as Diagraming Techniques for Analysts and Programmers, by James Martin or systems design texts by Ed Yourdon, Larry Constantine and others. Basic Principles A data flow diagram models the movement of information through a data processing system. A system is divided up into the following components: - External Entities are places where data enters or leaves the system. - Processes are the actual data processing steps. - Data Stores hold data while it is between processing steps. - Data Flows show the movement of data items between the system components. Data flow diagrams show the overall structure of a complex system and the relationships between system components. A materials processing facility such as an oil refinery is a good physical analogy to a data processing system. It may be modeled by a data flow diagram. Raw materials flow into the refinery from terminals, such as pipelines and barges. Holding tanks function as stores of materials. The raw materials are then transformed into finished goods by a number of processing steps. The finished goods leave the refinery through terminals. All of the components are interconnected by pipes through which flow materials in various stages of processing. 4 Data Flow Diagrams Oil Refinery Data Flow Diagram Materials Data Flow Terminal External Entity Holding Tank Data Store Processing Step Process Figure 2-1 is a data flow representation of a simple oil refinery created with Personal CASE. The modeling of physical systems such as a refinery is very similar to data flow modeling of a data processing system. Personal CASE can be used (with appropriate interpretation) as a tool for these applications as well. (Illustration omitted from text file) A Typical Model Figure 2-2 is a simple customer invoicing data processing system diagrammed with Personal CASE. Note the similarities to the oil refinery model. (Illustration omitted from text file) Data originates from external entities such as a customer phone order. The end results of the system are also external entities such as printed invoices and reports. Various types of processing are done with the information, each processing step transforming inputs into outputs. Intermediary results are placed in data stores until they can be processed. Data flows show the movement of data between the components of the system. Components The four components of a diagram are represented by standard symbols: (Illustration omitted from text file) The identity of each component is established by both a label and a description. Labels are short identifiers for each component. A description gives a more detailed explanation of the purpose of the component. This descriptive information is stored in a data dictionary. Whenever a label is used, the accompanying descriptive text is automatically supplied by Personal CASE and placed within the symbol on the page. Data Flow Diagrams 5 Multi-page Diagrams Many system designs are too complex to be expressed in a single data flow diagram. Such designs are best expressed as a hierarchy of related diagrams. A hierarchical organization of diagrams expands the details of a complex processing step into an entire sub-diagram on a different page. The first page of a hierarchical design presents an overview of the primary processing steps. Each subsequent page expands one of the processes on a higher level page to a greater level of detail. A process on a sub-diagram may further expand into additional detail on another diagram page. This hierarchical relationship of diagram pages follows the well-established systems design techniques of top-down design and hierarchical decomposition. An example of a hierarchical design is shown by the two diagram pages in Figure 2-4 and Figure 2-5. Personal CASE allows a system design to be decomposed into any number of pages. Hypertext links are maintained between the pages of a diagram to allow rapid movement within the hierarchy. (Illustrations omitted from text file) Personal CASE Reports In addition to the data flow diagram, a number of tabular reports are useful to the designer. These reports are derived from the relationships between diagram components. Personal CASE supplies the following reports: - Process Details lists each defined process along with its input and output data flows. - Process Hierarchy lists a "bill of materials" of all sub- processes that make up each process according to the hierarchical structure of the design. - Data Flow Usage lists the source and destination of all data flow relationships. - Dictionary Listing lists all identification and descriptive information found in the data dictionary for a design.