Structured System Analysis & Design

Structured System Analysis & Design

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Dharmendra Arora

Contents 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. JIM

What is Information? What is a System? What is System Design? What is System Analysis? Thus SAD is… Information System Some Bits From History Implications The animal called SSAD… So How do we develop an information system? More On SSAD Waterfall Model Major Elements of SSAD Benefits of SSAD Drawbacks Snapshot of RAD Which approach is better? Dharmendra Arora

What is information?

The simple most definition- Information is processed data presented in a meaningful manner.

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What is a System? A system is a collection of elements or components that are organised for a common purpose. Solar System • Computer System • Operating System •

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What is System Design? It is the process of planning a new system or one to replace or complement an existing system. To do so one must thoroughly understand the old system & determine how it can be made operationaly more efficient (say by computerisation). This is essentially the concept of System Analysis. JIM

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What is System Analysis?

It is all about gathering & interpreting facts, diagnosing problems and using information to recommend improvement.

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Thus SAD is…

Cleary System Analysis & Design (SAD) refers to the process of examining a business situation and improving it through better procedures & methods.

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Information System a collection of all the elements or components organised to manage information. predominantly in industry term information system depicts “software system meant to furnish some specific information need”.

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Some Bits From History In the early days of large scale information systems development many organisations used the Cobol programming language together with indexed sequential files to build systems for customer billing, payroll, stock control and a variety of other business areas. These developments at this time were characterised by :limited user involvement; inadequate requirements elicitation; use of ad hoc analysis and design techniques; absence of CASE support for analysis and design; time consuming use of 3GL tools; inflexible file and 3rd generation database management systems.

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Implications Frequently the results of this approach were systems which, on delivery, did not satisfy business requirements. This caused extensive maintenance requirements and thus an increase in the applications backlog. A variety of problems may have caused the mis-match between system functionality and business requirements :a lack of ownership of and commitment to the system from users as a result of the low level of involvement; business requirements may have changed between inception and delivery; requirements may have been mis-understood; inadequate analysis and design tools and techniques may have been used; or more likely a combination of these problems.

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The animal called SSAD… The response from the information systems community to these problems was the development of structured methodologies. To fully understand large complex system (in popular terms here we are talking about software system) Structured System Analysis & Design (SSAD) adopts a prescriptive approach to information systems development in that it specifies in advance the modules, stages and tasks which have to be carried out, the deliverables to be produced and furthermore the techniques used to produce the deliverables. It facilitates better control in the entire process.

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So How Do We Develop An Information System?

System Requirement Gathering Designing of System Development Testing Implementation

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SYSTEM DEVELOPMENT LIFE CYCLE

Preliminary Investigation (Feasibility)

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More On SSAD SSADM adopts the Waterfall model of systems development, where each phase has to be completed and signed off before subsequent phases can begin. It’s a strictly unidirectional process, like a waterfall from top to bottom.

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Waterfall Model START Preliminary Investigation (Feasibility)

Structured Analysis

System Requirement Gathering Designing of System

Structured Design

Development Testing Implementation JIM

STOP

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Major Elements of SSAD. Structured Analysis-focus on what system does or what is it required to do, not on how it should be done. Graphical Description Data Flow Diagrams Data Dictionary

Structured Design-focus on the development of software specificaiton. Graphical Description-flow charts

Languages that support SSAD- BASIC, Cobol, C etc. (basically all the procedural languages) JIM

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Benefits of SSAD Improved project management & control More effective use of experienced & inexperienced development staff Proper documentation makes project resilient to the loss of staff Enable projects to be supported by Computer based tools such as CASE Establishes a framework for good communication among the participants of the project. Develop better quality systems. JIM

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Drawbacks Because of its strict top-down unidirectional nature, it does not cater to the changes in the needs, after analysis phase. Specific concentration on software development not on implementation. Thus it is in contrast to the popular methodology called Rapid Application Development (RAD). JIM

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Snapshot of RAD

START

Preliminary Investigation (Feasibility)

Detailed requirements Prototyping Iterative phases Re-use of software components Rapid schedule Less formal reviews and communication Embraces Object Orientation Languages that follow RAD-java, C++

System Requirement Gathering Designing of System Development Testing Implementation STOP

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Which Approach Is Better?

?? JIM

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THANKS

Dharmendra Arora [email protected]

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