Principles of User Centred Design Howell Istance.
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Transcript of Principles of User Centred Design Howell Istance.
Principles of User Centred Design
Howell Istance
Some definitions
Human-Computer Interaction a discipline concerned with the design, evaluation
and implementation of interactive computing systems for human use and with the study of the major phenomena surrounding them
User Interface any boundary between the human user and the
computer system (includes documentation and training material)
not restricted to screens, keyboards and mice
User Centered Design
all systems need not be designed to suit everyone...
.... but should be designed around the needs and capabilities of those people who will use them
usability - concerned with making systems easy to learn, easy to use and efficient to use
Think about a car... how much knowledge about a car do you to be able to
drive it? do the best designed cars give the driver the most
information about the engine, suspension, etc? good design of the interface to the car includes designing
controls that are obvious to use behave in the way you expect give fast feedback are comfortable to use hide unnecessary information from the user
Misconceptions about user interface design a usable system has lots of
functions ‘I know it’s a bit hard to use but it’s
all described in the Help system’ ‘I know it works - I’ve got the
people in the office (or on the course) to use it’
Visibility, mapping and affordance
visibility: the correct parts must be visible, they must convey the correct message - that message is conveyed by signals
mapping: the relationship between what you want to do and what appears to be possible - good design exploits natural and easily perceived mappings
affordance: the perceived and actual properties of a thing, primarily those fundamental properties that determine just how the thing could possibly be used
Perspectives on design
think ‘design first, implementation second’ design the interface first for usability, only
compromise in the design for ease of implementation later if necessary
think how the system and interface should support what the user wants to do, rather than what the system is capable of doing
Implications for the design process
early focus on users and tasks clear understanding of what particular usability
attributes are important testing of prototypes of the design from an early
stage in the process results from prototype testing need to be used to
modify the design, which is retested software tools are needed to support this process - to
enable designs to be built and modified with little programming overhead
Waterfall model of S/W development
certainly better than no model at all, but too rigid requirements change during design process testing occurs late in the process
requirements analysis & definition
System and software design
implementation and unit testing
integration and system testing
operation & maintenance
Prototyping Model of S/W development
requirements definition
quick design
build prototype
evaluate and refine requirements
engineer product
Prototyping Model of S/W development
Advantages evaluation at an early stage prototype can be used to explore further
requirements
Disadvantages quick design may be badly founded building prototypes may not necessarily be rapid
Components in a user centred design
Product requirements (including usability specification)
Usability Specifications
Usability - extent to which application is easy to learn, easy to use and efficient to use
specification - defining what constitutes success in terms of measurable quantities
e.g ‘90 % of first-time users (without prior training) will be able to retrieve the shelf number of a given book within 300% of the time it would take an expert user to do so’(possible example from a library information system)
Knowledge of users
- general psychology
-characteristics of user groups
Product requirements (including usability specification)
Users
Subject of next lecture
Knowledge of users
- general psychology
-characteristics of user groups
Knowledge of users’ tasks and information requirements
Product requirements (including usability specification)
Tasks
Task Analysis involves study of the work users do, the component tasks within this and the information needed to complete each task
Object of interface design is to fit the design (content, navigation) around these task needs
Several different methods of capturing this Important to represent the analysis so that its
correctness maybe checked with groups of users
Knowledge of users
- general psychology
-characteristics of user groups
Knowledge of users’ tasks and information requirements
Knowledge of environment in which application will be used
Product requirements (including usability specification)
Environment
In general terms this refers to the physical and organisational environment
physical - location (e.g home, railway station, public libray) and the constraints this places on design solutions
organisational - usually an issue when introducing systems into businesses - systems need to fit the way in which they will be used
Knowledge of users
- general psychology
-characteristics of user groups
Knowledge of users’ tasks and information requirements
Knowledge of environment in which application will be used
Product requirements (including usability specification)
Knowledge of design principles - HCI, graphics, typography
Design principles Important to know what design guidance is available
and use what is already known design can not proceed by recipe, principles of good
practice can be given to the designer who needs to apply these HCI principles - quality of user-computer dialogue Graphics Design - means of effective and aesthetic
visual communication Typography - effective and aesthetic use of style in
text
Knowledge of users
- general psychology
-characteristics of user groups
Knowledge of users’ tasks and information requirements
Knowledge of environment in which application will be used
Product requirements (including usability specification)
Knowledge of design principles - HCI, graphics, typography
Knowledge of delivery platform and I/O devices
Knowledge of users
- general psychology
-characteristics of user groups
Knowledge of users’ tasks and information requirements
Knowledge of environment in which application will be used
Product requirements (including usability specification)
Knowledge of design principles - HCI, graphics, typography
Knowledge of delivery platform and I/O devices
Produce prototype
Prototypes
Early prototypes usually paper-based, used to quickly capture ideas
Later prototypes built on a machine to give a realistic ‘mock-up’ of what the final application will look like Should have sufficient functionality to enable
interactive testing before final version is available
Knowledge of users
- general psychology
-characteristics of user groups
Knowledge of users’ tasks and information requirements
Knowledge of environment in which application will be used
Product requirements (including usability specification)
Knowledge of design principles - HCI, graphics, typography
Knowledge of delivery platform and I/O devices
Produce prototype
Evaluate prototype though structured testing
Evaluation
‘expert’ based appraisal based on walk-throughs of the design in the context of completing selected tasks
subject based testing where people representative of the user population are observed completing selected tasks with the prototype
emphasis as much on qualitative data as on quantitative data