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Analysis I

Analysis I. Analysis. do. Carry out. use. Carry out. Validation. use. use. Identify the parts. People . Verification. depends on. Tools. Methods. Points of View. Verification Are we building the thing right? (compared to other products) among models. Validation

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Analysis I

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  1. Analysis I

  2. Analysis do Carry out use Carry out Validation use use Identify the parts People Verification depends on Tools Methods Points of View

  3. Verification Are we building the thing right? (compared to other products) among models Validation Are we building the right thing? (regarding stakeholders/users desire) Between the UofD and a Model Verification vs Validation

  4. Analysis • Identify the parts • How is it organized? • How is it stored? • traceability • Verification • formal • reuse domains • inspections

  5. Analysis • Validation • Close to the users/stakeholders • informal • prototyping (mock up, storyboard)

  6. Analysis Loop UofD Facts gathering communication * model ** yes problems? problems communication No * modeling ** identifying the parts model

  7. Identification of the parts • Depends on how the models are organized and stored • Linked to modelling and elicitation • 90% of the problems is in 10% do system

  8. Validation • Are we building the right product? • We have to compare the UofD with users/stakeholders expectations • Run Scenarios (Reading them in meetings) • Prototype

  9. Validation Strategies • Informal corroboration • storyboards • prototypes

  10. Validating through scenarios use • As many times as possible • The earliest the better • If possible validate the candidate scenarios list • Scenario Validation goal: elaborate the DEO list( Discrepancies, Errors and Omissions) • Users’ commitment is essential

  11. Validation Through Scenarios • Gradual confirmation of scenarios parts (objective, actors, resources) • Feedback for LEL • Tag scenarios where doubts arise • Make notes of discrepancies, errors or omissions

  12. Main stream • Validate scenarios with users using semi-structured interviews • Strategies: • Read scenarios aloud together with users • Ask if they have anything to add or change • Ask Why

  13. Storyboard [Leffingwell & Widrig] • Elicit reaction such as “Yes, but…” • Passive, Active or iterative • Identify actors, explain what happens to them and describe how it happens • More effective to projects with innovative or unknown content

  14. Storyboard • Pros: • cheap • User friendly, informal and iterative • Allow to criticize system interface early in the project • Easy to create and modify

  15. Types of storyboard • Passive • Static screens • Business rules • Reports • Active • Presentation (As in PowerPoint) • animation • simulation • Iterative • demo ( free browsing) • Iterative presentation

  16. Storyboard passive active iterative presentation screen prototype animation demo Business Rules simulation Iterative Presentation reports Complexity and cost

  17. Prototype • Prototypes are partial implementation to help stakeholders, users and developers to better understand system requirements

  18. Prototypes • Also helps to elicit reactions such as “ Yes, but…” • Help to clarify fuzzy requirements • Requirements that are known but not well defined or not well understood • Help elicit reactions such as “Now that I can see it working it comes to me that I also need…..” • Availability of tools that help to build fast and cheap prototypes

  19. Types of Prototypes [Davis] • Throw away • It has to work • Use any means to implement the desired result (it does not care for quality code) • Once the requirements are elicited the prototype is deleted • Evolving • Implemented using the same architecture being used in the system • The system may be an evolution of this prototype

  20. Prototype Vertical X Horizontal • Horizontal • Implements a large portion of the functionality • Vertical • Implement a few functions • Better quality

  21. Verification • Are we building the product correctly ? • Use of Models • representations/languages • Use of formalisms • Informal Techniques

  22. Use of formalisms • Formal Proofing of a model • Theorem proofing • Detection of discrepancies between the model and the meta models • Model Proofing

  23. Techniques • Inspection A formal evaluation technique in which artifacts are examined in detail by a person or group other than the author to detect errors, violations of development standards, and other problems. Formal, initiated by the project team, planned, author is not the presenter. • Walkthrough A review process in which a developer leads one or more members of the development team through a segment of an artifact that he or she has written while the other members ask questions and make comments about technique, style, possible error, violation of development standards, and other problems. Semi-formal, initiated by the author, quite frequently poorly planned.

  24. Walk through • ad hoc preparation • Meeting (author(s), evaluator(s), secretary) • Reading • author reads • Evaluators hear • Evaluators point out problems (questions) • Secretaries write down problems • List of problems

  25. Inspections • Create in 1972 by Fagan, at IBM, to improve quality of code • Currently they are used to check any type of artefact used in the software development process • Inspection can detect between 30% and 90% of existing errors • Reading techinique applied to an artefact aiming at detecting errors in the artefact according to a pre-stablished criterea

  26. Inspections

  27. Inspections in requirements • based on check lists: • Inspectors use a list with the itens to be checked • Each artifact has an specific list (req. Document, Use cases, Lexicon, Scenario, DfD, Class diagram ...) • Defects are anotated in the artifact being analysed • After reviewing, a meeting is carrried out to communicate the problems found to developers • Defects that can be found: • Incorrect sintax in the artifacts(Definition of a term, measrument units ...) • Incosistent information among artifacts (ex: Use cases and Glossary) • NFRs not explicited • Actors or resources incomplete or in excess • No Pre-conditions (Use Case and Scenarios) • No exceptions in scenarios

  28. DFD • Checklist DFD • The documentation should contain: • Date, numbered pages, list of topics, change and version control • Process represented by a numbered circle • Identifier should begin with a verb • Maximum number of processes should be 7 +- 2

  29. OO • Checklist OO: • Are all classes represented using rectangles with 1, 2 or 3 compartments? • Are there two classes with the same name? • Are there classes without defined relationships? • Are the attributes and methods for each class adequate? • All the Use Cases have corresponding Sequence Diagrams ? • Coupling and Cohesion are adequate ?

  30. N-Fold Inspection • Many teams • Each one carries out an independent inspection process • Compare results • Final Report

  31. User Moderator Leaders Team 3 Team 2 Team 1 Each document is revised by n teams where each team uses the inspection process to find errors Figura N-fold

  32. Parallel is better • Multiple inspection teams find more defects than one single bigger team • The teams tend to find sub sets of different defects • The combination of the various results from the different teams tends to sum instead of being redundant • Follow up • Release the document • Owner and moderator Key lessons in achieving widespread inspection use - Grady & Slack - IEEE Software, July1994, pp.46-57

  33. Challenges from inspections • Big Requirements Document • Informal and incremental revisions during the development of specification • Each inspector starts from a different point • Divide into many small teams – each team inspects a specific part of the document

  34. Challenges from inspections • Large inspection teams • Difficult to schedule meetings • Parallel conversation • Difficult to get an agreement • What to do? • Be sure the participants are there to inspect and not to “spy” the specification or to keep a political status

  35. Challenges from inspections • Large inspection teams • Understand which point of view (client, user, developer) the inspector is using and keep only one to each interested part • Establish many small teams and carry out the inspection in parallel. Combine the lists and remove redundancies.

  36. Challenges from inspections • Geographical distance between inspectors • videoconference, teleconference, e-mail, web • Difficult to observe corporal language and expressions, • Difficult to moderate • 25% reduction on the effectiveness • [Wiegers98] - The seven deadly sins of software reviews - Software Development -6(3) pp.44-47

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