© copyright de montfort university 2003 all rights reserved interactive design sept 03 john t burns...

© Copyright De Montfort University 2003 All Rights ReservedInteractive Design Sept 03 John T Burns

Interactive Systems Design & Evaluation

• John Burns• e-mail [email protected]

• 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


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


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


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


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!!


Getting it wrong!

• Some examples of bad design– The ATM– The Car Park Ticket Machine– The Hi - Tec Shopping Trolley– The Photocopier


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


Organisational Factors Environmental Factors

Task Factors

The UserHealth and Safety

Factors

Constraints

Comfort

Factors

System Functionality

Productivity Factors

User Interface


Justifying HCI

• Poor interface design can lead to – Increased errors– User frustration– Poor system performance– User rejection


Justifying HCI

• Good Interface design will provide – Fail-safe systems– Competitive advantages– Financial rewards– Increased efficiency– User satisfaction and enjoyment


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


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


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


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


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


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’


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


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


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


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


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


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


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.

© copyright de montfort university 2003 all rights reserved interactive design sept 03 john t burns...

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