22-10-2012, 01:31 PM
Structured Analysis and Structured Design
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Definition of Structured analysis
•“Structured analysis is a set of techniques and graphical tools that allow the analyst to develop a new kind of system specification that are easily understandable to the user. Analysts work primarily with their wits, pencil and paper.”
History of SASD
•Developed in the late 1970s by DeMarco, Yourdon, and Constantine after the emergence of structured programming.
•IBM incorporated SASD into their development cycle in the late 1970s and early 1980s.
•Classical SASD was modified due to its inability to represent real-time systems.
•In 1989, Yourdon published “Modern Structured Analysis”.
Philosophy of structured analysis and design
•Analysts attempt to divide large, complex problems into smaller, more easily handled ones. “Divide and Conquer”
•Top-Down approach (Classical SA), or Middle-Out (Modern SA)
•Functional view of the problem. “Form follows function”
•Analysts use graphics to illustrate their ideas whenever possible.
•Analysts must keep a written record.
Goals of SASD
•Improve Quality and reduce the risk of system failure
•Establish concrete requirements specifications and complete requirements documentation
•Focus on Reliability, Flexibility, and Maintainability of system
Drivers Behind SASD Creation
•Prior to SASD, requirements were documented through text rather than graphically.
•Large problem decomposition.
•Reduces redundancies.
“If the automobile followed the same development as
the computer, a Rolls-Royce would today cost $100,
get a million miles per gallon, and explode once a year
killing everyone inside.” Robert Cringley
Statement of Purpose - Example
•“The purpose of the credit card system is to provide a means for the company to extend credit to the customer. The system will handle details of credit application, credit management, billing, transaction capture, remittance, and management reporting. Information about transactions should be available to the corporate accounting system.”