Defining the Problem - Goals and requirements

Defining the Problem - Goals and requirements

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  Presented By: Mrs. R.NancyBeaulah, Asst. Professor, Dept. of Computer Science (SF), V.V.Vanniaperumal College for Women (Autonomous), Virudhunagar.
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   Requirements tospecify goals & Requirements  Concise Statement of the problem  Constraints exists for its solution  Goals are targets for achievement.  Goals apply both to development process and Work products.  Goals can be either qualitative or quantitative.
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   A QualitativeProcess goal:  The development process should enhance the professional skills of quality assurance personnel.  A Quantitative Process goal:  The system should be delivered with in 12 months.  A Qualitative Product goal:  The system should make user’s jobs more interesting.  A Quantitative Product goal:  The system should reduce the cost of a transaction by 25 percent.
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   Goals commonto all Project & Product:  Every project should be useful, reliable, understandable and cost-effective.  Every development process should deliver work products with in time and cost estimates.  It should provide a opportunity to develop new skills for the project personnel.  Some other goals like transportability, early delivery of subset capabilities and ease of use depends on the project.
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   Requirements specifythe capabilities provided by the software to solve the problem.  Requirements include  Functional Requirements  Performance Requirements  Requirements for the hardware, software, firmware and interfaces.  Requirements specify the development standards to both project and product.
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   Phase accuracyshall be with in 0.5 degrees.  Response to external interrupts shall be 0.25 seconds maximum.  System shall reside in 50k bytes of primary memory, excluding buffers.  System shall be fully operational 95% of each 24 hour period.  Whenever possible requirements must be quantified and can be used during acceptance testing.
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   Accuracy shallbe sufficient to support mission.  System shall provide real time response.  System shall make efficient use of primary memory.  System shall be 99% reliable.  The requirements said above are meaningless and often results in misunderstandings and disagreements between developers and customers.
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   It isdifficult to specify the quantitative requirements during planning phase.  At that stage it is not clear what is needed to solve the problem or what can be achieved within solution constraints.  But efforts should be taken to specify quantitative requirements and methods to verify that.
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   High levelgoals and requirements are often expressed in terms of quality attributes.  This can be translated in to specific requirements for any problem.  Example:  Reliability can be expressed in terms of source code accuracy, robustness, completeness and consistency.
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   High levelacceptance criteria should be specified during planning phase.  Lack of clearly stated quantified acceptance criteria leads to major misunderstanding between the developer and customer.  Acceptance criteria should be specified in terms of inspections, analysis and tests performed on the work products.  Each requirements should be specified along with the methods used to verify it.
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   The goalof delivering product in time can be expressed in terms of series of Milestones.  A milestone is a significant event in software product life cycle.  Examples of Milestones are completion of requirement analysis, completion of design and integration and successful testing of components.  Consideration of these issues leads to Life Cycle Models.
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   Software EngineeringConcepts,Richard Fairley