Human Computer Interaction

1. Chapter-6 HCI in the software process Human Computer Interaction

2. HCI in the software process • Software engineering and the design process for interactive systems • Usability engineering • Iterative design and prototyping • Design rationale

3. Usability is about creating effective user interfaces (UIs). • This interface is clearly graphical. It’s mouse-driven – no memorize or typing complicated commands. • It’s even what-you-see-is-what-you-get (WYSIWYG) – the user gets a preview of the award that will be created.

4. the software lifecycle • Software engineering is the discipline for understanding the software design process, or life cycle • Designing for usability occurs at all stages of the life cycle, not as a single isolated activity • In development of software product, we consider two main parties: • The customer who requires the use of product • The designer who must provide the product

5. Requirementsspecification Architecturaldesign Detaileddesign Coding andunit testing Integrationand testing Operation andmaintenance The waterfall model

6. Activities in the life cycle Requirements specification designer and customer try capture a description of what the system is expected to provide can be expressed in natural language or more precise languages, such as a task analysis would provide. The executable languages for software are less natural and are more closely to a mathematical language Architectural design high-level description of how the system will provide the services required factor system into major components of the system and how they are interrelated needs to satisfy both functional and nonfunctional requirements

7. Activities in the life cycle some classic examples of non-functional requirements are efficiency, reliability, timing and safety features of the system Detailed design The designer must provide a sufficiently detailed description so that they implemented in some language. The detailed design is a refinement of component description provided by architectural design

8. Coding and testing The detail design for a component of system should be in form that it is possible to implement it in some programming language. After coding, the component can be tested to verify that it performs correctly, according to some test criteria that were determined in earlier activities. Integration and Testing Once enough components have been implemented and tested, they must be integrated. Further testing is done to ensure correct behavior.

9. Maintenance involves the correction of errors in the system which are discovered after release and the revision of system services to satisfy requirements that were not realized during previous development.

10. The formality gap Real-worldrequirementsand constraints Verification and validation Verification designing the product right  Validation designing the right product  The formality gap means validation will always rely to some extent on subjective means of proof Management and contractual issues design in commercial and legal contexts

11. Requirementsspecification Architecturaldesign Detaileddesign Coding andunit testing Integrationand testing Operation andmaintenance The life cycle for interactive systems cannot assume a linearsequence of activities lots of feedback!

12. Usability engineering • The emphasis for usability engineering is in knowing exactly what criteria will be used to judge a product for its usability • The ultimate test of usability based on measurement of user experience • Usability engineering demands that specific usability measures be made explicit as requirements

13. Usability specification • usability attribute/principle • measuring concept: which makes the attribute more concrete by describing it in terms of the actual product • measuring method: how the attribute will be measured • now level: indicates the value for measurement with existing system • worst case: providing clear distinction b/w what will be acceptable and what will be unacceptable in final product

14. Usability engineering • planned level: target for the design • best case: agreed the best possible measurement Problems • usability specification requires level of detail that may not be possible early in design • satisfying a usability specification does not necessarily satisfy usability

15. part of a usability specification for a VCR • Attribute: Backward recoverability • Measuring concept: Undo an erroneous programming sequence • Measuring method: Number of explicit user actions to undo current program • Now level: No current product allows such an undo • Worst case: As many actions as it takes to program-in mistake • Planned level: A maximum of two explicit user actions • Best case: One explicit cancel action

16. ISO usability standard 9241 adopts traditional usability categories: • effectiveness • can you achieve what you want to? • efficiency • can you do it without wasting effort? • satisfaction • do you enjoy the process?

17. some metrics from ISO 9241 • Usability Effectiveness Efficiency Satisfaction objective measures measures measures • Suitability Percentage of Time to Rating scale for the task goals achieved complete a task for satisfaction • Appropriate for Number of power Relative efficiency Rating scale fortrained users features used compared with satisfaction with an expert user power features Learnability Percentage of Time to learn Rating scale for functions learned criterion ease of learning • Error tolerance Percentage of Time spent on Rating scale for errors corrected correcting errors error handling successfully

18. Iterative design and prototyping • Requirements for interactive system cannot be completely specified from beginning of life cycle • Only way to be sure about some features of potential design is to build and test them out on real users • The design can then be modified to correct any false assumptions that were revealed in the testing • This is the essence of iterative design

19. Iterative design and prototyping • Prototypes: iterative design is described by the use of prototypes, artifacts that simulate or animate some features of intended system • different types of prototypes • Throw-away: the prototype is built and tested • Incremental: There is one overall design for the final system • Evolutionary: fits in well with the modifications which must be made to the system that arise during the operation and maintenance activity in life cycle

20. Iterative design and prototyping • Management issues • time • planning • non-functional features • contracts

21. Techniques for prototyping • Storyboards need not be computer-based can be animated • Limited functionality simulations some part of system functionality provided by designers tools like HyperCard are common for these • High-level programming support Hypertalk was an example of special-purpose high-level programming language which makes it easy for designer to program certain features of an interactive system

22. Warning about iterative design • Two problems: • It is often the case that design decisions made at very beginning of the prototyping process are wrong • Second problem is slightly more subtle, and serious. If in the process of evaluation, a potential usability problem is diagnosed, it is important to understand the reason from the problem and not just detect the symptom.

23. Design rationale • In designing any computer system, many decisions are made as the product goes from a set of vague customer requirements to a deliverable entity. • Often it is difficult to recreate, or rationale, behind various design decisions. • Design rationale is information that explains why a computer system is the way it is. • Design rationale allow designer to manage the information about the decision-making process, in terms of when and why design decisions were made.

24. Benefits of design rationale: • communication throughout life cycle • reuse of design knowledge across products • enforces design discipline • organizes potentially large design space • capturing contextual information

25. Design rationale • There are some issues that distinguish various techniques in terms of usability • Two types • Process-oriented design rational • interested in recording an historical accurate description of a design team making some decision on a particular issue for the design • It is also intended to preserve the order of deliberation and decision making for a particular product, placing less stress on generalization of design for use b/w different products

26. Structured oriented design rational: • Is less interested in preserving the historical evolution of the design • Rather, it is more interested in providing the conclusion of the design activity • Two examples: • Issue-based information system (IBIS) • Design space analysis

27. Issue-based information system (IBIS) • main elements: Issues (or Questions) – hierarchical structure with one ‘root’ issue Positions (or Ideas) – potential resolutions of an issue Arguments (Pros and Cons) – modify the relationship between positions and issues • gIBIS is a graphical version – Compendium

28. structure of gIBIS • Issues, positions and arguments are nodes in the graph and the connections between them are labeled to clarify the relationship b/w adjacent nodes • For example, an issue can suggest further sub-issues, or a position can respond to an issue or an argument can support a position • The gIBIS structure can be supported by a hypertext tool to allow a designer to create and browse various parts of design rationale

29. supports Position Argument responds to Issue responds to objects to Position Argument specializes Sub-issue generalizes questions Sub-issue Sub-issue structure of gIBIS

30. IBIS Elements in Compendium

31. Dialogue Mapping in IBIS The situation: A finance data mart is updated overnight through a batch job that takes a few hours. This is good enough for most purposes. However, a small (but very vocal!) number of users need to be able to report on transactions that have occurred within the last hour or so – waiting until the next day, especially during month-end, is simply not an option. The dev team had to figure out the best way to do this. The location: Dev Team’s office. The players: two members from IT, one from finance. The shared display: Compendium running on my computer, visible to all the players. The discussion was launched with the issue stated up-front: How should we update our data mart during business hours? IT people in the dev team came up with several ideas to address the issue.

32. Dialogue Mapping in IBIS

33. Dialogue Mapping in IBIS

34. Design space analysis • This approach embodied in the ……. • QOC – hierarchical structure: questions (and sub-questions) – represent major issues of a design options – provide alternative solutions to the question criteria – the means to assess the options in order to make a choice • DRL – similar to QOC with a larger language and more formal semantics

35. the QOC notation • The design space is initially structured by a set of questions representing the major issues of the design • Questions in a design space analysis are similar to issues in IBIS • The QOC technique advocates the use of general criteria

36. the QOC notation Criterion Option Question Option Criterion Option Criterion ConsequentQuestion … … Question

37. Psychological design rationale • to support task-artefact cycle in which user tasks are affected by the systems they use • aims to make explicit consequences of design for users • designers identify tasks system will support • scenarios are suggested to test task • users are observed on system • negative aspects of design can be used to improve next iteration of design

38. Summary The software engineering life cycle • distinct activities and the consequences for interactive system design Usability engineering • making usability measurements explicit as requirements Iterative design and prototyping • limited functionality simulations and animations Design rationale • recording design knowledge • process vs. structure