Modern Systems Analysis
and Design
Third Edition
Jeffrey A. Hoffer
Joey F. George
Joseph S. Valacich
Chapter 15
Finalizing Design
Specifications
15.1
Copyright 2002 Prentice-Hall, Inc.
Learning Objectives
 Discuss the need for system design
15.2
specifications
 Define quality requirements and write quality
requirements statements
 Read and understand a structure chart
 Distinguish between evolutionary and
throwaway prototyping
 Explain the role of CASE tools in capturing
design specifications
 Demonstrate how design specifications can
be declared for Web-based applications
Introduction
Need for systems to be developed more
quickly today
The lines between analysis and design and
design and implementation are blurring
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
15.3
Traditional approaches allowed for a break
between design and implementation
Other approaches, such as CASE and
prototyping, have caused overlap between the two
phases
The Process of Finalizing
Design Specifications
Less costly to correct and detect errors during
the design phase
Two sets of guidelines


Writing quality specification statements
The quality of the specifications themselves
Quality requirement statements
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15.4
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Correct
Feasible
Necessary
Prioritized
Unambiguous
Verifiable
The Process of Finalizing
Design Specifications
Quality requirements
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15.5
Completely described
Do not conflict with other requirements
Easily changed without adversely affecting
other requirements
Traceable back to origin
The Process of Finalizing
Design Specifications
Deliverables and Outcome

Set of physical design specifications
 Contains detailed specifications for each part of
the system
15.6
Representing Design
Specifications
Traditional Methods
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Pre-CASE
Documents written natural language and
augmented with graphical models
Specification documents
 Figure 15-2 shows an example
 Several methods for streamlining
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15.7
Computer-based requirements tools
Prototyping
Visual development environments
Representing Design
Specifications
Structure Charts
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15.8
Shows how an information system is
organized in hierarchical models
Shows how parts of a system are related to
one another
Shows breakdown of a system into
programs and internal structures of
programs written in third and fourth
generation languages
Representing Design
Specifications
Structure Charts

Module
 A self-contained component of a system, defined by a
function
 One single coordinating module at the root of structure
chart
 Single point of entry and exit
 Communicate with each other by passing parameters
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
15.9
Data couple
 A diagrammatic representation of the data exchanged
between two modules in a structure chart
Flag
 A diagrammatic representation of a message passed
between two modules
Representing Design
Specifications
Structure Charts

Module
 Special Symbols
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15.10
Diamond
 Only one subordinate will be called
Curved Line
 Subordinates are called repeatedly until terminating
condition is met
Predefined modules
Hat
 Subordinate module is important logically but code is
contained in superior module
Representing Design
Specifications
Structure Charts

Pseudocode
 Method used for representing the instructions
inside a module
 Language similar to computer programming
code
 Two functions
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15.11
Helps analyst think in a structured way about the
task a module is designed to perform
Acts as a communication tool between analyst and
programmer
Representing Design
Specifications
Prototyping


Construction of the model of a system
Allows developers and users to
 Test aspects of the overall design
 Check for functionality and usability
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Iterative process
Two types
 Evolutionary Prototyping
 Throwaway Prototyping
15.12
Representing Design
Specifications
Prototyping

Evolutionary Prototyping
 Begin by modeling parts of the target system
 If successful, evolve rest of the system from the
prototype
 Prototype becomes actual production system
 Often, difficult parts of the system are
prototyped first
 Exception handling must be added to prototype
15.13
Representing Design
Specifications
Prototyping

Throwaway Prototyping
 Prototype is not preserved
 Developed quickly to demonstrate unclear
aspect of system design
 Fast, easy to use development environment
aids this approach
15.14
Representing Design
Specifications
Prototyping

Oracle Designer: An Example
 Transforming and Generating the Database
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15.15
Entity-Relationship Diagramming Tool
Database Design Transformer Tool
Server Model Diagram
End Result
 Generation of Data Definition Language (DDL)
scripts
Create database by running scripts
Representing Design
Specifications
Prototyping

Oracle Designer: An Example
 Transforming and Generating Software
Modules
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15.16
Data Flow Diagram
Functional Hierarchy Diagram
Application Design Transformer
 Transforms diagrams into software modules
which can be used to generate forms or reports
Generate form or report in Design Editor
Radical Methods: eXtreme Programming
Short cycles
Incremental planning approach
Automated tests
Utilizes two-person programming team
Planning, analysis, design and construction
are fused together into one phase
Requirements and specifications are uniquely
captured
15.17
Radical Methods: eXtreme Programming
Planning game

Players
 Business
 Development

Story cards
 Description of procedure or system feature
15.18
Radical Methods: eXtreme Programming
Planning game

Three phases
 Exploration
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Business creates a story card
Development responds with time estimate
 Commitment
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Business sorts story cards into three stacks
Development sorts story cards according to risk
Business selects cards to include in next release of
product
 Steering
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15.19
Business monitors development activity
Radical Methods: eXtreme Programming
Iteration Planning Game
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Played by programmers
Task Cards
 Several task cards generated for each story card
 Three phases
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Exploration
 Story cards converted to task cards
Commitment
 Programmers accept responsibility for tasks
Steering
 Programmers write code, test it and integrate it
 Game takes place during time between intervals of
planning game steering phase meetings
15.20
Radical Methods: RAD
Four life-cycle phases
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Planning
Design
Construction
Cutover
Iteration between design and
construction
15.21
Electronic Commerce
Application
Microsoft FrontPage used to build
throwaway prototype
Template based HTML
15.22
Summary
Types of Design Specifications
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Written document augmented by various
diagrams
Structure chart
Computer-based requirements
management tool
Prototypes
 Throwaway versus Evolutionary
15.23
Summary
Radical Methods
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eXtreme Programming
RAD
Electronic Commerce Application
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15.24
Throwaway prototyping