–Executable software (software development life cycle)
–Computer Aided Business Systems (systems development life cycle)
Basic Systems/Software Development Steps:
Define the problem… essential first step (initiating systems development)
–What is the problem?
–Work: compile problem statement or vision statement. Define objectives. Define Scope.
–Output: terms of reference for continuation
Feasibility (systems investigation)
–Expand on problem. Is there a feasible solution? How do we develop a new system?
–Work: High level analysis. Cost Benefit analysis. Organisational Feasibility. Technology available. Development and implementation plan (high level).
–Output: Feasibility report. Summary of preliminary findings and recommendations for next step.
Systems Analysis
–Understand what is done now. What are the requirements of a new system.
–Work: Analyse existing system’s ability to meet user’s needs. Determine what problems are, what the requirements are.
–Output: System model. Statement of requirements
Systems Design (two steps)
–How in general can the system be designed and realised
–Work: transform the requirements into a logical design. Prepare designs for various options.
–Output: alternative design options
Detailed Design
–How specifically should the system be designed and implemented
–Work: prepare a detailed physical design (architecture, hardware, data organisation, detailed design software procedures) for the chosen solution
–Output: detailed design specification
Implementation
–Realise the new system (put it into operation)
–Work: buy or assemble or develop programs. Write procedures. Set up organisation. Install hardware. Test. Convert from old system. Go live.
–Output: an operational system
Operation, Maintenance & Review
–Use the system, evaluate, modify if necessary, keep system in operation.
–Work: day to day running, modifications and maintenance
–Output: an ongoing operational system
Define the problem… essential first step (initiating systems development)
–What is the problem?
–Work: compile problem statement or vision statement. Define objectives. Define Scope.
–Output: terms of reference for continuation
Feasibility (systems investigation)
–Expand on problem. Is there a feasible solution? How do we develop a new system?
–Work: High level analysis. Cost Benefit analysis. Organisational Feasibility. Technology available. Development and implementation plan (high level).
–Output: Feasibility report. Summary of preliminary findings and recommendations for next step.
Systems Analysis
–Understand what is done now. What are the requirements of a new system.
–Work: Analyse existing system’s ability to meet user’s needs. Determine what problems are, what the requirements are.
–Output: System model. Statement of requirements
Systems Design (two steps)
–How in general can the system be designed and realised
–Work: transform the requirements into a logical design. Prepare designs for various options.
–Output: alternative design options
Detailed Design
–How specifically should the system be designed and implemented
–Work: prepare a detailed physical design (architecture, hardware, data organisation, detailed design software procedures) for the chosen solution
–Output: detailed design specification
Implementation
–Realise the new system (put it into operation)
–Work: buy or assemble or develop programs. Write procedures. Set up organisation. Install hardware. Test. Convert from old system. Go live.
–Output: an operational system
Operation, Maintenance & Review
–Use the system, evaluate, modify if necessary, keep system in operation.
–Work: day to day running, modifications and maintenance
–Output: an ongoing operational system
Implementation of the SDLC
-“Traditional approach,” also known as the Waterfall Model
-Rapid Prototyping
-Incremental Approach
-Extreme Programming
Waterfall Model Advantages
By far the most commonly used approach up to now
All the most widely used methods are underpinned by the waterfall model
The stages are clear cut
Activities -> Outputs
By far the most commonly used approach up to now
All the most widely used methods are underpinned by the waterfall model
The stages are clear cut
Activities -> Outputs
Requirements Analysis -> Feasibility Study, Outline Requirements
Requirements Definition -> Requirements Specification
System Specification -> Functional Specification, Acceptance Test Specification, Draft user manual
Architectural Design -> Design architecture specification, System test specification
Interface Design -> Interface specification, Integration test specification
Detailed Design -> Design Specification, Unit test specification
Coding -> Program Code
Unit Testing -> Unit test result report
Module Testing -> Module test result report
Integration Testing -> Integration test report, Final user manual
System Testing -> System test report
Acceptance Testing -> Final System
Waterfall Disadvantages
Can be too rigid
One phase must be completed before proceeding on to the next
Difficult to incorporate user feedback without implementation
Rapid Prototyping
One phase must be completed before proceeding on to the next
Difficult to incorporate user feedback without implementation
Rapid Prototyping
The prototype is an executable version of the functionality and interfaces (sometimes called a behavioural prototype)
Minimal time investment in prototypes
Facilitates user understanding and specification role
The prototype is a throwaway program and used to elicit and specify requirements (non-operational)
The system is then designed, constructed, and implemented using waterfall model
Rapid prototyping has been enabled by the availability of modern programming tools (screen painters, 4GLs, Database software, etc.)
Incremental
Planning
Management Cycle Plan: resource, execute, control
Planning means “thinking of everything”
Without a plan (defining some goal) it is impossible to evaluate how you are progressing toward that goal
Gantt Charts for Planning
Your Project
The SDLC gives you the stages you must follow to develop your program/system
You must plan how long you are going to take at each stage and what you are going to produce at each stage
Then you can evaluate how you are progressing (control)
Planning means “thinking of everything”
Without a plan (defining some goal) it is impossible to evaluate how you are progressing toward that goal
Gantt Charts for Planning
Your Project
The SDLC gives you the stages you must follow to develop your program/system
You must plan how long you are going to take at each stage and what you are going to produce at each stage
Then you can evaluate how you are progressing (control)
Conclusion
There is a recognised systematic approach to software development
The recognised steps are:
–Feasibility (investigation)
–Analysis
–Design
–Implementation (including testing)
–Maintenance and review
Each stage delivers outputs that progressively build the system
You can plan by assessing what you are going to deliver at each stage and how long you think it will take. You control, progress against the plan
The recognised steps are:
–Feasibility (investigation)
–Analysis
–Design
–Implementation (including testing)
–Maintenance and review
Each stage delivers outputs that progressively build the system
You can plan by assessing what you are going to deliver at each stage and how long you think it will take. You control, progress against the plan
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