Design Principles and Guidelines

• Introduction
• Usability Principles
• Heuristic and Golden Rules Based on material from: Sharp, H., Preece, J. and Rogers, Y. (2019). Interaction Design Beyond Human-Computer Interaction. 5th Ed. Sussex: John Wiley & Sons Ltd.

• Describe heuristic, golden rules and norman’s 7 principles
• Enable you to use/follow the rules in order to increase the usability of the system/product

Guidelines

(e.g. use colour to highlight links) Can guide/advise on how achieve a principle Narrowly focused.

Can be too specific, incomplete, & hard to apply BUT they are more general and lower in authority than Standards (e.g. use colour RGB #1010D0 on home links) which are very specific & high in authority.

• Principles: Example - usability principles by Dix et al (HCI book)
• Standards: They are often set by national (eg British Standards Institution) or international bodies (ISO). Example [of standards] - ISO 9241 "Ergonomic Requirements for Office Work with Visual Display Terminals (VDT)s"
• Guidelines: Example - Smith and Mosier's "Guidelines for User Interface Software" [MITRE Corporation 1986].

• Design rules should be used early in the lifecycle [e.g., during the design; note that they can also be used to evaluate the usability of the system]
• We will:
  • First look at abstract principles for supporting usability
  • Later on, we will look at the most well used and well known sets of heuristics or 'golden rules ‘, which tend to provide a succinct summary of the essential characteristics of good design (Nielsen's heuristics, Shneiderman's golden rules and Norman's principles

by Dix et al (HCI book)

Learnability - the ease with which new users can

1.

begin effective interaction and achieve maximal performance.

Flexibility - the multiplicity of ways the user and

2.

system exchange information.

Robustness - the level of support provided to the

3.

user in determining successful achievement and assessment of goal-directed behavior.

3. Robustness (cont)

• Task conformance - the extent to which the system services support all the tasks the user would wish to perform and in the way the user would wish to perform.

Jakob Nielsen’s 10 Usability Heuristics

• 4. Consistency and standards: users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.
• 5. Error prevention: even better than good error messages is a careful design which prevents a problem from occurring in the first place.
• 6. Recognition rather than recall: make objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

Jakob Nielsen’s 10 Usability Heuristics

• 7. Flexibility and efficiency of use: accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.
• 8. Aesthetic and minimalist design: dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

Jakob Nielsen’s 10 Usability Heuristics

• 9. Help users recognize, diagnose, and recover from errors: error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.
• 10. Help and documentation: even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

• https://www.nngroup.com/articles/ten-usability-heuristics/