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Requirements Validation

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Requirements Validation

  1. 1. Fundamentals Validation Techniques Assistance Techniques for Validation Summary Requirements Validation Antonio Villegas Ni˜o n avillegas@essi.upc.edu @avillegasn Requirements Engineering Facultat d’Inform`tica de Barcelona a April 4, 2011 C CC BY: $ Antonio Villegas Requirements Validation April 4, 2011 1 / 29
  2. 2. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryOutline 1 Fundamentals 2 Validation Techniques 3 Assistance Techniques for Validation Antonio Villegas Requirements Validation April 4, 2011 2 / 29
  3. 3. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryThe context of Requirements Validation Antonio Villegas Requirements Validation April 4, 2011 3 / 29
  4. 4. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryThe context of Requirements Validation Antonio Villegas Requirements Validation April 4, 2011 3 / 29
  5. 5. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsRequirements Validation Validation (in requirements engineering) Validation denotes checking whether inputs, performed activities, and created outputs (requirements artifacts) of the requirements engineering core activities fulfil defined quality criteria. Validation is performed by involving relevant stakeholders, other requirement sources (standards, laws, etc.) as well as external reviewers, if necessary. Antonio Villegas Requirements Validation April 4, 2011 4 / 29
  6. 6. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsQuality Gateway Antonio Villegas Requirements Validation April 4, 2011 5 / 29
  7. 7. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsQuality Criteria Completeness - The requirement must contain all relevant information (template). Consistency - The requirements must be compatible with each other. Adequacy - The requirements must address the actual needs of the system. Unambiguity - Every requirement must be described in a way that precludes different interpretations. Comprehensibility - The requirements must be understandable by the stakeholders. Antonio Villegas Requirements Validation April 4, 2011 6 / 29
  8. 8. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsQuality Criteria Importance - Each requirement must indicate how essential it is for the success of the project. Measurability - The requirement must be formulated at a level of precision that enables to evaluate its satisfaction. Necessity - The requirements must all contribute to the satisfaction of the project goals. Viability - All requirements can be implemented with the available technology, human resources and budget. Traceability - The context in which a requirement was created should be easy to retrieve. Antonio Villegas Requirements Validation April 4, 2011 7 / 29
  9. 9. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsExamples Train doors shall be opened as soon as the train is stopped at a platform Antonio Villegas Requirements Validation April 4, 2011 8 / 29
  10. 10. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsExamples Ambiguity Train doors shall be opened as soon as the train is stopped at a platform Possible interpretations: The front of the train is (stopped) at a platform? or The whole train is (stopped) at a platform? Antonio Villegas Requirements Validation April 4, 2011 8 / 29
  11. 11. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsExamples Contradiction Train doors must always be kept closed between stations. and elsewhere... Train doors must be opened once a train is stopped after an emergency signal. Antonio Villegas Requirements Validation April 4, 2011 9 / 29
  12. 12. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsRisk of insufficient validation Quality Assurance Antonio Villegas Requirements Validation April 4, 2011 10 / 29
  13. 13. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsRisk of insufficient validation Antonio Villegas Requirements Validation April 4, 2011 11 / 29
  14. 14. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryMotivation and GoalsRisk of insufficient validation The earlier an error is discovered, the cheaper it is to correct. Antonio Villegas Requirements Validation April 4, 2011 12 / 29
  15. 15. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrinciples of ValidationThe 6 Principles of Validation First Principle: Involving the Right Stakeholders Ensure that relevant company-internal as well as relevant external stakeholders participate in validation. Pay attention to the reviewers’ independence and appoint external, independent stakeholders, if necessary. Second Principle: Defect Detection vs. Defect Correction Separate defect detection from the correction of the detected defects. Antonio Villegas Requirements Validation April 4, 2011 13 / 29
  16. 16. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrinciples of ValidationThe 6 Principles of Validation First Principle: Involving the Right Stakeholders Ensure that relevant company-internal as well as relevant external stakeholders participate in validation. Pay attention to the reviewers’ independence and appoint external, independent stakeholders, if necessary. Second Principle: Defect Detection vs. Defect Correction Separate defect detection from the correction of the detected defects. Antonio Villegas Requirements Validation April 4, 2011 13 / 29
  17. 17. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrinciples of ValidationThe 6 Principles of Validation Third Principle: Leveraging Multiple Independent Views Whenever possible, try to obtain independent views that can be integrated during requirements validation in order to detect defects more reliably. Fourth Principle: Use of Appropriate Documentation Formats Consider changing the documentation format of the requirements into a format that matches the validation goal and the preferences of the stakeholders who actually perform the validation. Antonio Villegas Requirements Validation April 4, 2011 14 / 29
  18. 18. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrinciples of ValidationThe 6 Principles of Validation Third Principle: Leveraging Multiple Independent Views Whenever possible, try to obtain independent views that can be integrated during requirements validation in order to detect defects more reliably. Fourth Principle: Use of Appropriate Documentation Formats Consider changing the documentation format of the requirements into a format that matches the validation goal and the preferences of the stakeholders who actually perform the validation. Antonio Villegas Requirements Validation April 4, 2011 14 / 29
  19. 19. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrinciples of ValidationThe 6 Principles of Validation Fifth Principle: Creation of Development Artefacts during Validation If your validation approach generates poor results, try to support defect detection by creating development artefacts such as architectural artefacts, test artefacts, user manuals, or goals and scenarios during validation. Sixth Principle: Repeated Validation Establish guidelines that clearly determine when or under what conditions an already released requirements artefact has to be validated again. Antonio Villegas Requirements Validation April 4, 2011 15 / 29
  20. 20. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrinciples of ValidationThe 6 Principles of Validation Fifth Principle: Creation of Development Artefacts during Validation If your validation approach generates poor results, try to support defect detection by creating development artefacts such as architectural artefacts, test artefacts, user manuals, or goals and scenarios during validation. Sixth Principle: Repeated Validation Establish guidelines that clearly determine when or under what conditions an already released requirements artefact has to be validated again. Antonio Villegas Requirements Validation April 4, 2011 15 / 29
  21. 21. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryValidation Techniques Inspections Desk-Checks Walkthroughs Prototypes Antonio Villegas Requirements Validation April 4, 2011 16 / 29
  22. 22. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryInspectionsInspections Inspection: an organized examination process of the requirements. Involved roles: Critical Success Factors: Organizer Commitment of the organization Moderator Size and complexity of the inspected artefacts Author Number and experience of the Inspectors inspectors Minute-taker Benefit: Detailed checking of the artefacts Effort: Medium-High Antonio Villegas Requirements Validation April 4, 2011 17 / 29
  23. 23. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryDesk-ChecksDesk-Checks 1 The author of a requirement artefact distributes the artefact to a set of stakeholders. 2 The stakeholders check the artefact individually. 3 The stakeholders report the identified defects to the author. 4 The collected issues are discussed in a group session (optional). Critical Success Factors: Benefit: Obtain feedback Commitment of the participants from individual reviewers Coverage of all the aspects Not recommended for critical artefacts Effort: Medium Antonio Villegas Requirements Validation April 4, 2011 18 / 29
  24. 24. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryWalkthroughsWalkthroughs A walkthrough does not have formally defined procedure and does not require a differentiated role assignment. Checking early whether an idea is feasible or not. Obtaining the opinion and suggestions of other people. Checking the approval of others and reaching agreement. Critical Success Factors: Benefit: Validation of Involving stakeholders from ideas and sketches different contexts Comprehensible presentation of the artefact Effort: Medium-Low Antonio Villegas Requirements Validation April 4, 2011 19 / 29
  25. 25. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPrototypesPrototypes A prototype allows the stakeholders to try out the requirements for the system and experience them thereby. 1 Develop the prototype (tool support). 2 Training of the stakeholders. 3 Observation of prototype usage. 4 Collect issues. Critical Success Factors: Benefit: Effort Highly effective defect detection Level of detail of the Proof of feasibility prototype Quality of the review Effort: Very High-High Antonio Villegas Requirements Validation April 4, 2011 20 / 29
  26. 26. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryReviewReview of Techniques Inspection Desk-Check Walkthrough Prototype Goal extensive search for less-detailed check feedback on early try out the defects in a of a larger extent sketches of an requirements and manageable extent of artefacts artefact experience them of requirements individually artefacts Group session yes, strict focus on optional yes, for providing yes, to evaluate the defect collection feedback observation Process detailed roles and defined but flexible no predefined defined but flexible strict steps procedure Effort for Medium-High Medium Medium-Low Very High-High execution Benefit for High Medium Low Very High validation Antonio Villegas Requirements Validation April 4, 2011 21 / 29
  27. 27. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryAssistance Techniques for Validation Checklists Perspective-based Reading Creation of Artefacts Antonio Villegas Requirements Validation April 4, 2011 22 / 29
  28. 28. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryChecklistsChecklists A checklist should comprise few questions so that the reviewer can use it during validation in an effective way. Applicable with each validation technique. Create different checklists for different validation goals Create checklists based on rules, experience, and defect statistics. Critical Success Factors: Benefit: Limiting the size of the checklists Each reviewer knows how to check the artefact Avoiding generic questions such as ”Are the requirements complete?” Used for validation and for elicitation Considering the stakeholders’ background and experience Effort: Low-Very Low Antonio Villegas Requirements Validation April 4, 2011 23 / 29
  29. 29. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryPerspective-based ReadingPerspective-based Reading Applying perspective-based reading during requirements validation means checking the same set of artefacts by reading them from different perspectives. Applicable with each validation technique. Identify the perspectives that are relevant for the project For each perspective, provide reading instructions and questions that support defect detection. Critical Success Factors: Benefit: Quality of the instructions and Practical support for questions reviewers Experience of the reviewers More defects uncovered than without perspectives Involving stakeholders from different contexts Effort: High-Medium Antonio Villegas Requirements Validation April 4, 2011 24 / 29
  30. 30. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryCreation of ArtifactsCreation of Artifacts Creating artefacts during validation means using the requirements to be checked as a reference for creating other development artefacts. Applicable with each validation technique. Verbalisation of Models. Creating Scenarios, Test Cases, a User Manual... Benefit: Critical Success Factors: Defects uncovered during Quality of the created artefacts artefacts creation Experience of the reviewers Reuse of the created Traceability between requirements artefacts as initial drafts and artefacts Effort: High-Medium Antonio Villegas Requirements Validation April 4, 2011 25 / 29
  31. 31. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryReviewReview of Assistance Techniques Checklists Perspective-based Creation of Reading Artifacts Goal guide the checking the same validate the stakeholders during set of artefacts by requirements while the requirements reading them from creating drafts of validation different artefacts perspectives Critical Success size and diversity of quality of the quality and Factors the checklists instructions and traceability of the experience of the artefacts reviewers Effort for execution Low-Very Low High-Medium High-Medium Benefit for validation Medium Medium High-Medium Antonio Villegas Requirements Validation April 4, 2011 26 / 29
  32. 32. Fundamentals Validation Techniques Assistance Techniques for Validation SummarySummary The Context of Requirements Validation in RE The Quality Gateway and Quality Criteria Risk of Insufficient Validation The 6 Principles of Validation Validation Techniques Assistance Techniques for Validation Antonio Villegas Requirements Validation April 4, 2011 27 / 29
  33. 33. Fundamentals Validation Techniques Assistance Techniques for Validation Summary “Quality is never an accident. It is always the result of intelligent effort.” John Ruskin Antonio Villegas Requirements Validation April 4, 2011 28 / 29
  34. 34. Fundamentals Validation Techniques Assistance Techniques for Validation SummaryReferences Denger, C. and Olsson, T. Quality Assurance in Requirements Engineering Pohl, K. Requirements Engineering: Fundamentals, Principles, and Techniques. Part V. Validation pp. 509-585 van Lamsweerde, A. Requirements Engineering: from system goals to UML models to software specifications. Chapter 5. Requirements Quality Assurance pp. 187-217 Robertson, S. and Robertson, J. Mastering the Requirements Process. 2nd Edition. Chapter 11. Antonio Villegas Requirements Validation April 4, 2011 29 / 29

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