Design Rules-Part B Standards and Guidelines Material from Authors of Human Computer Interaction Alan Dix, et al

Overview Design rules in the form of standards and guideline to provide direction Essential characteristics of good design Design patterns for a generative approach to capture/reuse design knowledge

Standards Usually set by national & international bodies Apply to HW and SW in interactive systems Different characteristics of HW & SW affect utility of design underlying theory HW – physiology or ergonomics SW – psychology or cognitive science (more vague) change HW – difficult/expensive to change SW – flexible

ISO Standard 9241 Example Pertains to usability specification and applies to HW and SW design Defines usability as The effectiveness, efficiency and satisfaction with which specified users achieve specified goals in particular environments Goes on to define effectiveness, efficiency and satisfaction Definitions important as they give us ideas of how to measure usability.

Strength of Standards Lies in ability to force large communities to abide (so-called authority) Most standards are suggestions Some practices become de facto standards before formalization

Guidelines Not rules, suggestions The more abstract the guideline, the more it resembles a principle outlined in 7.2 The more specific, the more suited it is to detailed design Even more useful, if they can be automated to translate detailed design into implementation

Guidelines for Interactive Design …or interface design Smith and Mosier (Mitre) 6 basic categories data entry, data display, sequence control, user guidance, data transmission, data protection broken into more specific subcategories Example: Data Entry position designation distinctive cursor – movable, visual feature (shape, blink, etc.) : See also 1.1-17 Distinctive multiple cursors allows cross-referencing

Guidelines for Interactive Design Mayhew more recent, comprehensive, general guidelines in a catalog

Guidelines Dialog styles question and answer, form-filling, menu selection, function keys, command language, query, natural language, direct manipulation Most guidelines applicable for implementation of any one of dialog styles in isolation Must also consider mixing of styles in an application (Mayhew provides guidelines on this)

Specific Guidelines Apple’s HCI Guidelines: the Apple Desktop Interface Abstract principle in Apple guidelines is consistency Effective applications are both consistent within themselves and consistent with one another. More concrete guideline ‘noun-verb’ ordering – user selects an object on desktop, then the operation

Dialog Initiative Under general usability category of flexibility principle The user, not the computer, initiates and controls all actions Involves a trade-off user freedom vs system protection

GUI Systems Guidelines on how to adhere to abstract principles for usability in programming environment Style guides OpenLook Open Software Foundation Motif GUI involve using toolkits with high-level widgets each have own look-and-feel promote consistency

OpenLook example For design of menus Suggestion for grouping items in the same menu “Use white space between long groups of controls on menus or in short groups when screen real estate is not an issue.” Justification: more options on a menu, longer it takes user to locate and point to item Careful: grouping logically related items like saving and deleting files may result in a simple slip in pointing

Golden Rules (Heuristics) Broad-brush design rules, may not be applicable in every case Shneiderman’s 8 Golden rules of interface design convenient and succinct used in design, but can be used for evaluation relate to abstract principles

Shneiderman’s 8 Golden rules of interface design Strive for consistency Enable frequent users to use shortcuts Offer informative feedback Design dialogs to yield closure Offer error prevention and simple error handling Permit easy reversal of actions Support internal locus of control so user is in control Reduce short-term memory load

Norman’s 7 Principles for Transforming Difficult Tasks into Simple Ones Use both knowledge in world and in the head Simplify the structure of tasks Make things visible – bridge gulfs of execution and evaluation Get mappings right Exploit the power of constraints Design for error. When all fails, standardize. (when no natural mappings)

HCI Patterns Approach to capture and reuse knowledge Patterns abstract essential details of successful design, so they can be applied again in new situations. Originated in architecture Used in software development to capture solutions to common programming problems More recently in interface and web design

HCI Patterns A Pattern Pattern states A Wizard Pattern ‘go back to safe place’ example in Figure 7.3 Pattern states the problem the solution the rationale where pattern came from what context it applies in example illustrating the pattern references to other patterns (which may be needed to complete it) A Wizard Pattern