chapter15 finalizing design specifications
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Copyright 2002 Prentice-Hall, Inc.
Modern Systems Analysisand Design
Third Edition
Jeffrey A. Hoffer Joey F. George
Joseph S. Valacich
Chapter 15Finalizing Design
Specifications
15.1
Learning ObjectivesDiscuss the need for system design specificationsDefine quality requirements and write quality
requirements statementsRead and understand a structure chartDistinguish between evolutionary and throwaway
prototypingExplain the role of CASE tools in capturing design
specificationsDemonstrate how design specifications can be
declared for Web-based applications
15.2
Introduction
Need for systems to be developed more quickly todayThe lines between analysis and design and design and implementation are blurring Traditional approaches allowed for a break
between design and implementation Other approaches, such as CASE and prototyping,
have caused overlap between the two phases
15.3
The Process of Finalizing Design Specifications
Less costly to correct and detect errors during the design phaseTwo sets of guidelines Writing quality specification statements The quality of the specifications themselves
Quality requirement statements Correct Feasible Necessary Prioritized Unambiguous Verifiable
15.4
The Process of Finalizing Design Specifications
Quality requirements Completely described Do not conflict with other requirements Easily changed without adversely affecting
other requirements Traceable back to origin
15.5
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 Pre-CASE Documents written natural language and
augmented with graphical models Specification documents
Figure 15-2 shows an example Several methods for streamlining
Computer-based requirements tools Prototyping Visual development environments
15.7
Representing Design Specifications
Structure Charts 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
15.8
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
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
15.9
Representing Design Specifications
Structure Charts Module
Special Symbols 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
15.10
Representing Design Specifications
Structure Charts Pseudocode
Method used for representing the instructions inside a module
Language similar to computer programming code
Two functions 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
15.11
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
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 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
15.15
Representing Design Specifications
Prototyping Oracle Designer: An Example
Transforming and Generating Software Modules
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
15.16
Radical Methods: eXtreme Programming
Short cyclesIncremental planning approachAutomated testsUtilizes two-person programming teamPlanning, analysis, design and construction are fused together into one phaseRequirements 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 Business creates a story card Development responds with time estimate
Commitment 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 Business monitors development activity
15.19
Radical Methods: eXtreme Programming
Iteration Planning Game Played by programmers Task Cards
Several task cards generated for each story card Three phases
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 Planning Design Construction Cutover
Iteration between design and construction
15.21
Electronic Commerce Application
Microsoft FrontPage used to build throwaway prototypeTemplate based HTML
15.22
Summary
Types of Design Specifications Written document augmented by various
diagrams Structure chart Computer-based requirements
management tool Prototypes
Throwaway versus Evolutionary
15.23
Summary
Radical Methods eXtreme Programming RAD
Electronic Commerce Application Throwaway prototyping
15.24
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