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The Original Shareware (WeMake CDs)(Volume 1.1)(CDs, Inc)(1993).iso
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INTRO1.TXT
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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 WindowsÆ data presentation and interaction abilities in
a powerful and straightforward fashion.
You donÆt 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 UserÆs 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.