1. Chapter 15 Finalizing Design Specifications
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.

2. Learning Objectives Discuss the need for system design 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
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3. Introduction Need for systems to be developed more quickly today
The 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
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4. 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
Correct
Feasible
Necessary
Prioritized
Unambiguous
Verifiable
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5. 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
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6. The Process of Finalizing Design Specifications
Deliverables and Outcome
Set of physical design specifications
Contains detailed specifications for each part of the system
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7. 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
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8. 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
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9. 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
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10. 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
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11. 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
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12. 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
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13. 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
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14. 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
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15. 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
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16. 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
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17. 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
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18. Radical Methods: eXtreme Programming
Planning game
Players
Business
Development
Story cards
Description of procedure or system feature
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19. 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
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20. 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
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21. Radical Methods: RAD Four life-cycle phases
Planning
Design
Construction
Cutover
Iteration between design and construction
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22. Electronic Commerce Application
Microsoft FrontPage used to build throwaway prototype
Template based HTML
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23. Summary Types of Design Specifications
Written document augmented by various diagrams
Structure chart
Computer-based requirements management tool
Prototypes
Throwaway versus Evolutionary
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24. Summary Radical Methods Electronic Commerce Application
eXtreme Programming
RAD
Electronic Commerce Application
Throwaway prototyping
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