Goals of Human-Computer Interaction

• Create usable software-enabled products and user-interfaces.
• Enhance the usability of existing products
• Identify problems and tasks (such as in the workplace) that can be addressed with software products

Dimensions of usability

Preece, Rogers and Sharp provide one of the more comprehensive lists for defining usability (p. 14):

• Effectiveness (very general concept, too vague)
• Efficiency (alt term: ease of use)
• Safety
• Utility (alt term: usefulness)
• Learnability (alt term: ease of learning)
• Memorability

Safety and memorability do not appear on many people's lists. Effectiveness seems to be one of the most abused usability terms.

Most authors also include user satisfaction as an important usability goal (also called attitude or likeability). Note that Preece, Rogers and Sharp cover this dimension under User Experience Goals in section 1.5.2.

HCI practitioners need to be mindful of other practical considerations when designing their products. These include the impact of legacy systems, portability and reliability.

Elementary design principles

• Visibility
• Feedback
• Constraints
• Mapping
• Consistency
• Affordance

Many of these principles are addressed in Nielsen's heuristic evaluation (see section 1.6.1 in the text).

Discussion items:

• What are examples of software-enabled interactive products?
• What are examples of tasks that have been automated by software products? How has technology changed the nature of these tasks?
• Identify products with usability problems. To which usability objectives (i.e. learnability, efficiency, etc.) do the problems correspond?
• Often usability objectives have inherent tradeoffs. What are examples? For example, in which situations might improving learnability negatively affect efficiency?
• How do the listed design principles support usability goals? Do some design principles support particular goals?