Robert Biddle Carleton University Canada

1. ExtremeSystem ProgrammingMetaphor Robert BiddleCarleton UniversityCanada Rilla Khaled, Pippin Barr James NobleVictoria University of WellingtonNew Zealand

2. Outline • XP & System Metaphor • Peircian Semiotics: • Modeling Metaphor • XP Practice: • Choosing a Metaphor • Evaluating a Metaphor

3. Agile Software Development • Individuals and interactionsover processes and tools • Working software over comprehensive documentation • Customer collaboration over contract negotiation • Responding to changeover following a plan

4. BeckXP: eXtreme Programming • Fine scale feedback • TestDrivenDevelopment (were UnitTests & AcceptanceTests) • PlanningGame • WholeTeam (was OnsiteCustomer) • PairProgramming • Continuous process rather than batch • ContinuousIntegration • DesignImprovement (was RefactorMercilessly) • SmallReleases • Shared understanding • SimpleDesign • SystemMetaphor • CollectiveCodeOwnership • CodingStandard or CodingConventions • Programmer welfare • SustainablePace (original name: FortyHourWeek)

5. XP System Metaphor • A story that everyone - customers, programmers and manager - can tell about how the system work. Beck • The metaphor just helps everyone on the project understand the basic elements and their relationships. Words chosen to identify technical entities should be consistently taken from the chosen metaphor. As development proceeds and the metaphor matures, the whole team will find new inspiration from examining the metaphor. Beck • The team had the benefit of a very rich domain model developed by members of the team in the project's first iteration. It gave the members of the project an edge in understanding an extremely complex domain. C3 Team • I still haven't got the hang of this metaphor thing. I saw it work, and work well, on the C3 project, but it doesn't mean I have any idea how to do it, let alone how to explain how to do it. Fowler

6. Basic Peircean Semiotics • Semiotics is the study of signs. • Charles Sanders Peirce developed a triadic model of the sign: • Object (or Referent): the concept or thing actually represented by the sign. • Representamen: the sign itself. • Interpretant: the result of an interpreter’s encounter with a sign.

7. Unlimited Semiosis

8. Eco’s Model Reader To make his text communicative, the author has to assume that the ensemble of codes he relies upon is the same as that shared by his possible reader. The author has thus to foresee a model of the possible reader (hereafter Model Reader) supposedly able to deal interpretatively with the expressions in the same way as the author deals generatively with them. Umberto Eco: The Role of the Reader, 1979

9. A Semiotic Model of Metaphor:Pierce, Lakoff & Johnson

10. Modeling MetaphorMetaphor Introduction

11. Modeling MetaphorMetaphorical Entailment A Metaphor is a Sign Generator

12. Entailment Linkage

13. XP System Metaphor

14. OOP Signs

15. Modeling MetaphorProgram Code Signs

16. MetaphorIntroduction XP System Metaphor Model MetaphoricalEntailment ProgramCode

17. Practice: Finding and EvaluatingMetaphorscape

18. A Bank Account is a Water Reservoir

19. Metaphor Introduction MetaphorscapeChoosing a Metaphor • Brainstorming Potential Metaphors • With referent, suggest representamen • Include team, customer, domain expert • Consider explaining system to non-expert • Consider surrounding metaphors • Select most promising n

20. Choosing a Metaphor II • Brainstorming Metaphorical Entailments • Choose metaphor • Identify entailments: referent and interpretant • Begin individually and then merge Metaphorical Entailments

21. Choosing a Metaphor III • Brainstorming Program Code Signs • Identify implied objects/classes • Determine usefulness of objects/classes • Correctness, consistency, coherence • Select useful, discard others Program Code

22. Conclusion • Beck: A story that everyone - customers, programmers and manager - can tell about how the system work. • Fowler: “This is a real gap in XP, and one that the XPers need to sort out”. • Our explorations: • Language: Vocabulary and Structure • Techniques: Based on OOD and HCI practice

23. ExtremeSystem ProgrammingMetaphor Robert BiddleCarleton UniversityCanada Rilla Khaled, Pippin Barr James NobleVictoria University of WellingtonNew Zealand

25. Web browser Web server E-commerce site Email client Space Invaders GPS handheld Blog software Payroll system Compiler Banking system Library Backup system PDA software CVS System Ideas

27. User-Interface Metaphor You can take advantage of people's knowledge of the world around them by using metaphors to convey concepts and features of your application. Use metaphors involving concrete, familiar ideas and make the metaphors plain, so that users have a set of expectations to apply to computer environments. (Apple Computer Inc., 1992) Familiar metaphors provide a direct and intuitive interface to user tasks. By allowing users to transfer their knowledge and experience, metaphors make it easier to predict and learn the behaviors of software-based representations. (Microsoft Corporation, 1995)

28. The Document Metaphor

29. Metaphor and Metaphorical Entailments • The data is an object. • The data can be written on. • The data can be read. • The data contains text, and possibly images and graphs, etc. • The data can be ripped. • The data can be typed up. • The data is usually on white paper. • The data can be photocopied. • The data can be written in pencil or pen or ink. • The data can (sometimes) be edited using twink or an eraser. • The data contains information. • The data can be set on fire. • The data can be picked up and moved from place to place. • The data can be thrown in a trashcan. • The data can give you a paper-cut. • …

30. XP System Metaphor • A story that everyone - customers, programmers and manager - can tell about how the system work. Beck • The metaphor just helps everyone on the project understand the basic elements and their relationships. Words chosen to identify technical entities should be consistently taken from the chosen metaphor. As development proceeds and the metaphor matures, the whole team will find new inspiration from examining the metaphor. Beck • The team had the benefit of a very rich domain model developed by members of the team in the project's first iteration. It gave the members of the project an edge in understanding an extremely complex domain. C3 Team • I still haven't got the hang of this metaphor thing. I saw it work, and work well, on the C3 project, but it doesn't mean I have any idea how to do it, let alone how to explain how to do it. Fowler

31. Evaluating a Metaphor • How is the Metaphor Good? • whether the entailments of the metaphor contain programmable ideas • whether the metaphor addresses the major system components and their known functionality. • whether the metaphor entailments provide a vocabulary with which to describe the system • Is the metaphor too poor? • which system components and interactions are left undescribed by the metaphor • Is the metaphor misleading? • whether the metaphorical entailments imply non-existent system components or non-existent behaviour.