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© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Interactive Systems Design & Evaluation
• John Burns• e-mail jtb@dmu.ac.uk
• W 5.6Recommended Text:HCI, J Preece et al, Addison Wesley, 2001Also:HCI, Dix, Finlay, Abowd & Beale, Prentice Hall, 1998Designing the User Interface, B Shneiderman, Addison
Wesley, 1998Newman & Lamming Interactive Systems Design 1995
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Objectives of this Lecture
• To outline what we mean by ID• To define HCI • To demonstrate the need for ISDE• To indicate the scope of ISDE• To consider some general principles of
HCI design• To place ISDE in the context of SD models
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
What is ISDE about?
• Interactive systems are designed to enable communication between the system and the user
• This takes place via the systems ‘user interface’• ISDE is concerned with:-
– Designing interactive systems to support human activities
– Applying usability engineering techniques to evaluate the effectiveness and appropriateness of the design
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
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
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
What is HCI
• HCI is concerned about :-– Finding out how people use computers– Trying to ensure that systems are designed
to closely match users’ needs– Ensuring that users can make sense of the
information that is presented to them– Ensuring that the user can
communicate/interact with the system• This is not always the case!!
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Getting it wrong!
• Some examples of bad design– The ATM– The Car Park Ticket Machine– The Hi - Tec Shopping Trolley– The Photocopier
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Getting it right!
• These illustrate 3 key factors that the designer needs to focus on– The user– The task – The environment
• Next slide shows other factors
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Organisational Factors Environmental Factors
Task Factors
The UserHealth and Safety
Factors
Constraints
Comfort
Factors
System Functionality
Productivity Factors
User Interface
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Justifying HCI
• Poor interface design can lead to – Increased errors– User frustration– Poor system performance– User rejection
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Justifying HCI
• Good Interface design will provide – Fail-safe systems– Competitive advantages– Financial rewards– Increased efficiency– User satisfaction and enjoyment
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
What makes for a good interface?
• A good interface will – Provide feedback– Provide easy reversal of actions (relieves
anxiety)– Give users feeling that they are in control– Reduce reliance on STM
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Think about a car...
• how much knowledge about a car do you need 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
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
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
• visibility indicates the mapping between the intended action and the actual operation
• affordance: the perceived and actual properties of a thing, primarily those fundamental properties that determine just how the thing could possibly be used
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Perspectives on design
• users are often not interested in the program and use it only as a tool to achieve some task in their work– give me £20 from my current account (ATM)– draw me a section of the valve called P1023 in a
place I can define (CAD system)– (games are an exception..)
• manufacturers are aware of the importance of usability...
• ... but often do not know how to design for usability and how to test or evaluate it effectively
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Continued perspectives...
• 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
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
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’
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
User Centred 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
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Implications for the design process
• there must be an early focus on users and tasks• there must be a clear understanding of what particular
usability attributes are important• to ensure usability targets can be met, there must be
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 and this is then retested - i.e. there are iterations in the design - test cycle
• software tools are needed to support this process - to enable designs to be built and modified with little programming overhead
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
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
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Prototyping Model of S/W development
requirements definition
quick design
build prototype
evaluate and refine requirements
engineer product
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
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
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
The Star Life Cycle
• evaluation relevant to all stages in life cycle• intended to be equally supportive of top-down and
bottom up development
Implementation
Prototyping Evaluation
Conceptual design/Formal design
RequirementsSpecification
Task Analysis/Functional Analysis
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Design Methods
• There is no single ‘golden’ design method that can ensure successful interactive design
• Requires designer to gain an understanding of the problem and apply appropriate techniques
• Fundamental to achieving success is the need to shift continually between two types of design activity
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Design Activities
• Analysis– During analysis we test the design to ensure it is
meeting our targets for usability and quality
• Synthesis– Here we shape the design drawing on fresh ideas,
previous experience and solutions to similar problems
© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns
Further Reading
• Chapters 1 & 2 Preece• The Psychology of Everyday things.
Norman D 1988 • Turn Signals are the Facial expressions of
Automobiles. Norman 1992. – Both books provide amusing and thought
provoking examples of bad designs in everyday life. He uses this as the basis to argue for the need for technology to be humanized.