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Systems Analysis_ Prototyping and Iteration by dffhrtcv3

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									    Systems Analysis,
Prototyping and Iteration
         Systems Analysis
This  is a process used in the design
 of new systems. Systems analysis
 follows stages of investigation, design
 and implementation.
Each stage should involve close
 consultation with potential users, in
 the various functional areas of the
 organisation, to ensure that their
 information and operational
 requirements are met.
The  design stage should produce a
 system specification, which should
 detail all necessary materials and
 procedures needed to fulfill the
 specification.
The specification should detail all
 the necessary clerical procedures,
 hardware requirements and the
 inputs, processing and outputs
 required of the computer software.
After   implementation of a system, it
 will require continual monitoring and
 probably, occasional modification,
 when the operational or information
 requirements of users change. This
 maintenance task is the responsibility
 of the systems analyst.
SDM Waterfall Model
Feasibility
    The feasibility study determines whether a
  particular development project should go ahead. If the
  project is to proceed then a project plan and budget
  estimate for the other stages of development will be
  produced.

Requirements analysis
    The requirements for the new or modified system
  are gathered at this stage. They should be recorded so
  that at the end of the project the software can be
  tested to ensure it fulfills the requirements.
Design specification
  Design focuses on:
    high level design, e.g. what programs are needed, what are their inputs and
    outputs, what are their interactions with other software or the operating
    system.
    low level design, e.g. how will the program work, what models or algorithms
    will be used, what libraries are required.
    data design, e.g. for input and output, data structures in the software.
   The level of detail in the design may be a matter of personal choice or may
    be specified by particular development procedures. Having a detailed design
    will make generating the code easier but will make changing things difficult
    whereas a more broad brush design will leave more work in the
    implementation phase but allows room for the details to come out as the
    development progresses. Above all the design should be documented
    including reasons for making particular choices if a number of options were
    available. This makes it much easier for new developers to join a project and
    helps when new features are required.
Coding
    In this phase the designs are translated into code.
  Programming tools such as compilers and quality assurance
  tools are used to generate good quality source code and the
  software application. Testing of small self-contained parts
  (modules) of the overall application may take place depending
  on the modularity of the code.
Testing
    The overall system is tested to ensure that it works on
  the intended platform(s), giving correct results or showing
  the required behaviour defined in the requirements
  document. The use of debuggers and profiling tools will be
  useful at this stage to identify errors in the code and get
  the best possible performance from the code. Optimum
  performance is especially important in scientific computing
  applications.
Maintenance
    Once the system is delivered to users it will
  inevitably need maintenance. There may be bugs
  caused by unexpected input values (add them to a
  test suite) or by unexpected (inappropriate) use of
  the software (tighten up the documentation). In
  addition users will want more or different
  functionality and will definitely want it to run
  faster or address bigger problems! The software
  development process should be able to
  accommodate changes at this stage through a well
  thought out design and any changes should have
  their own requirements, design, coding and testing
  stages.
In  the waterfall model, it is possible to rework
 earlier stages in the light of experience
 gained at a later stage. Each stage is signed
 off and the next stage is proceeded with.
 However the end user is rarely involved in the
 development stage, even though they may
 well be involved in signing off. It is therefore
 critical that the analysts and the programmers
 understand the end-users’ requirements.
 This can be quite difficult with the waterfall
 model.
The  waterfall model has disadvantages,
 which can be overcome using Prototyping, in
 which a model of the system is developed in
 partnership with the end-user. The features
 are worked out with the end user using a
 prototype, and the end user can have a
 considerable input into the development of a
 project.
Benefits are:

Misunderstandings   are detected at early
 stages
The user will notice any missing functions,
 incomplete or inconsistent requirements.
Can be built quickly to demonstrate systems
It can be used for training before the system
 is finished
Drawbacks are:
Project management can be
 uncoordinated or even sloppy.
Meetings with end users can become
 time consuming.
The final result could be completely
 different to what was requested in the
 first place.
Different Methods of Prototypes
Piloting – Test the feasibility of the design
 proposal
Modelling – building to develop an
 understanding of the user’s requirements
Throw-away prototyping – Pilot and modelling
 are throw away types – once they achieve their
 purpose the real system is built.
Evolutionary prototyping – each prototype built is
 a step closer to solution.

								
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