6. HCI in the software process


(a) How can design rationale benefit interface design and why might it be rejected by design teams? (b) Explain QOC design rationale using an example to illustrate.

answer available for tutors only

(a) It makes design decisions and the reasons for them explicit. It can be used to communicate decisions within the design team, to clients and to incoming new team members. It can allow re-use of design decisions in future designs. It forces rigour in the design process and helps designers to generate ideas. It can highlight trade-offs that are implicit in a decision.

It may be time consuming and may take resources away from the actual design. There is little tool support for DR commercially available. Designers can get wrapped up in doing DR rather than in the design. Those making the effort may not perceive themselves to be the ones gaining the benefit.

(b) QOC is an example of design space analysis, structure-oriented design rationale. This means that its primary concern is not with how a design decision was reached (in terms of the process) but why it was reached (in terms of a post-hoc representation of the design space). Designs are structured around Questions, each of which is answered by a number of Options, which in turn are supported or not supported by a range of Criteria. A Decision (the Option chosen in a given design) is represented by boxing the chosen Option or changing its labelling from O (for Option) to D (for Decision). Subsequent questions result from particular options being considered and chosen. QOC uses a semi-formal graphical notation to represent the design space in terms of these three features. (Answer would draw an example QOC showing a question with options and criteria - indicating the decision taken and ideally a subsequent question.)

Other exercises in this chapter

ex.6.1 (tut), ex.6.2 (tut), ex.6.3 (open), ex.6.4 (open), ex.6.5 (open), ex.6.6 (open)

all exercises for this chapter