Pr 005 qa_workshop

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Pr 005 qa_workshop

  1. 1. Software Engineering Prof.Dr.ir. F. GielenQuality Attribute Workshop Vakgroep Informatietechnologie – IBCN
  2. 2. Workshop Overview1. Build the Quality Attribute Tree2. Elaborate 3 quality attribute scenarios3. Map to architecture tacticsVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 2
  3. 3. Quality Attributes Quality Attributes are non functional requirements related to the ABC. They are documented using Quality Attribute Scenarios. (NOT in UML)Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 3
  4. 4. The Utility Tree Quality Attribute Challenges:  Characterizing, Quantification …  Selection & Priority The Utility tree is top-down approach for:  characterizing the quality attribute requirements – make them less abstract.  E.g. the system has to be fast …  selecting the most important quality goals to be the high-level nodes (performance, security, availability, modificability, maintanibility)  the leaves of the tree are quality scenarios evaluated by importance (success of the system) and difficulty (architect’s assessment).Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 4
  5. 5. Utility Tree Example ROOT LVL 1 LVL 2 LVL 3 Importance: Short Scenario: • business • Stimulus • technical • Context • ResponseVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 5
  6. 6. Generating a Quality Attribute Utility TreeQuality attributes are articulated in detail:Goal: Elicit the most important quality attributes as short scenarios. Root: Utility is an expression of the benefit to the user or customer. Level 1: Quality attributes are the second level. The initial set comes from the business drivers Level 2: Attribute Refinements. Level 3: Short scenarios (stimulus, context, response) Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 6
  7. 7. Lvl 2 : Attribute Refinement Make the quality attribute less abstract by characterizing them based on attribute taxonomies and generic QAS. Info can be found in standards (ISO 25010)  Example : PerformanceVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 7
  8. 8. LvL 3: Short Scenario Prioritisation1. Describe a number of short scenarios based on attribute refinements.2. Project decision makers give a relative ranking based on importance (business goal).3. Architect gives a ranking based on difficulty to satisfy the scenario. (technical goal)4. Each scenario has a (H,H), (H,M),…(L,M),(L,L) priority assigned.5. Based on this a selection of scenarios is made for the purpose of elaboration. Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 8
  9. 9. Example : JBOSS Quality AttributesVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 9
  10. 10. Workshop Overview1. Build the Quality Attribute Tree2. Elaborate 3 quality attribute scenarios3. Map to architecture tacticsVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 10
  11. 11. Generic QA Scenarios Performance QAS Every quality attribute has a generic scenario.  Itcontains the characteristics and the common vocabulary used to describe each of the sections in the specific QA scenario. Examples:  Performance  Modifiability  Usability  Security Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 11
  12. 12. Specific ScenariosA Quality Attribute Scenario describes:  SOURCE: who or what  STIMULUS: does something  ARTIFACT: to the system or part of it  ENVIRONMENT: under certain conditions  RESPONES: how the system reacts  MEASURE: how you can measure this Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 12
  13. 13. Performance Generic QAS ArtifactSource Stimulus Environment Response MeasureExternal Periodic Normal mode Change in LatencyInternal Sporadic Overload mode system Deadline Reduced mode Throughputevents Stochastic Capacity mode or Capacity Bursty service Jitter events level. Miss rate Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 13
  14. 14. Modifiabililty Generic QAS Artifact Code, Data, Interfaces Components, Resources, Configs ..Source Stimulus Environment Response MeasureDeveloper Modify: - Design - Change, # of artifactsSys - Functions - Build - Test Effortadmin - Deploy - Deploy Time - QualitiesUser - Runtime - Platform Cost - Technology Impact - Scale/Scope New defects Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 14
  15. 15. Example : Public Transport Signage Availability QAS :SOURCE who or what A random eventSTIMULUS does something ... causes a failureARTIFACT to the system or part of it ... to the communication systemENVIRONMENT under certain conditions ...during normal operationsRESPONSE how the system reacts All displays must start showing scheduled arrival times for all busesMEASURE how you can measure this ... Within 30 seconds of failure detection Q: What is the architectural impact of this requirement ? Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 15
  16. 16. Workshop Overview1. Build the Quality Attribute Tree2. Elaborate 3 quality attribute scenarios3. Map to architecture tacticsVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 16
  17. 17. Performance Tactics: Summary Performance Resource Resource Demand Resource ArbitrationEvent •Increase Management •Scheduling Response computationalArrives efficiency •Introduce generated •Reduce concurrency computational within •Maintain overhead multiple copies Time Constraints •Manage •Increase Event Rate available •Control resources Frequency of Sampling Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 17
  18. 18. Modifiability Tactics: summary Modifiability Reduce Defer Size Binding Time Split Increase Reduce Changes made,Change modules Cohesion CouplingRequest Tested and Deployed Increase EncapsulationArrives Semantic Wrap on Time, Coherence Restrict within Budget Abstract communication paths Common Services Use an intermediary Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 18
  19. 19. QAW: Quality Attribute Workshop1. Select the quality attributes that provide utility to the user. (lvl1): 1. Verify the generic QAS & ISO 250152. Refine the attributes of this quality (lvl2): 1. Verify attribute taxonomies (ISO25010)3. Provide short scenario’s (lvl3)4. Assign priorities to the scenarios.5. Elaborate the most important scenarios (6 parts) .6. Map to tacticsVakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 19
  20. 20. QAW Resources Quality Attributes Technical Report CMU/SEI- 95-TR-021 Summary of generic QA scenario’s ISO 25010 publication: SQuaRE quality model Vakgroep Informatietechnologie – Onderzoeksgroep IBCN p. 20
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