Design Rules-Part BStandards 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 Entryposition 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

1. Strive for consistency

2. Enable frequent users to use shortcuts

3. Offer informative feedback

4. Design dialogs to yield closure

5. Offer error prevention and simple error handling

6. Permit easy reversal of actions

7. Support internal locus of control so user is in control

8. Reduce short-term memory load

Norman’s 7 Principles

for Transforming Difficult Tasks into Simple Ones

1. Use both knowledge in world and in the head

2. Simplify the structure of tasks

3. Make things visible – bridge gulfs of execution and evaluation

4. Get mappings right

5. Exploit the power of constraints

6. Design for error.

7. 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 ‘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