Requirements Errors 2-Software Requirement-Lecture Slides, Slides of Software Project Management

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Requirements Errors – IILecture # 15

Today’s Topic and Recap• We discussed requirements errors inthe last lecture• Introduced different types of errors• Discussed defect prevention• Today we’ll talk about defect removaland in particular inspections using,perspective-based reading

Inspections - 1• Inspections, by all accounts, do a betterjob of error removal than anycompeting technology, and they do itat a lower cost– Robert Glass

Inspections - 2• Inspections are conducted by a group ofpeople working on the project, with theobjective to remove defects or errors• Every member of the inspection team has toread and evaluate requirements documentsbefore coming to the meeting and a formalmeeting is conducted to discussrequirements errors

Inspections - 4• A complete description of inspectionsmust address five dimensions:– Technical– Managerial– Organizational– Assessment– Tool support

Defect Detection WithoutInspectionsRequirements Design^ Coding^ Documentation

Testing^ Maintenance Requirements^ Design^ Coding

Documentation^ Testing^ Maintenance

Defect Origins Defect Discovery^

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Observations• Requirements engineers are trained to writerequirements documents, but have notraining on reading/reviewing requirementsdocuments• Reviewers typically rely on ad hoc readingtechniques, with no well-defined procedure,learning largely by doing

Techniques for ReadingRequirements Documents• Ad hoc review• Checklist review• Defect-based reading• Perspective-based reading

Checklist Review• A list of items is provided to reviewers,which makes this inspection processmore focused

Defect-based Reading• Provides a set of systematic proceduresthat reviewers can follow, which aretailored to the formal software costreduction notation

Different Perspectives - 1• PBR operates under the premise thatdifferent information in the requirements ismore or less important for the different usesof the document• Each user of the requirements documentfinds different aspects of the requirementsimportant for accomplishing a particulartask

Different Perspectives - 2• PBR provides a set of individual reviews,each from a particular requirements user’spoint of view, that collectively cover thedocument’s relevant aspects• This process is similar to constructingsystem use cases, which requires identifyingwho will use the system and in what way

Two Questions• What information in these documentsshould they check?• How do they identify defects in thatinformation?

Benefits of Different Perspectives - 1• Systematic– Explicitly identifying the different uses for therequirements gives reviewers a definiteprocedure for verifying whether those uses areachievable• Focused– PBR helps reviewers concentrate moreeffectively on certain types of defects, ratherthan having to look for all types