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