Week 8 - The process of interaction design

Prof. Ahmed Sameh

Overview

• What is involved in Interaction Design?– Importance of involving users– Degrees of user involvement– What is a user-centered approach?– Four basic activities

• Some practical issues– Who are the users?– What are ‘needs’?– Where do alternatives come from?– How do you choose among alternatives?

• A simple lifecycle model for Interaction Design

• Lifecycle models from software engineering

• Lifecycle models from HCI

What is involved in Interaction Design?

• It is a process:– a goal-directed problem solving activity informed by

intended use, target domain, materials, cost, and feasibility

– a creative activity– a decision-making activity to balance trade-offs

• It is a representation:– a plan for development– a set of alternatives and successive elaborations

Importance of involving users• Expectation management

– Realistic expectations – No surprises, no disappointments– Timely training– Communication, but no hype

• Ownership – Make the users active stakeholders– More likely to forgive or accept problems– Can make a big difference to acceptance

and success of product

Degrees of user involvement

• Member of the design team– Full time: constant input, but lose touch with

users– Part time: patchy input, and very stressful– Short term: inconsistent across project life– Long term: consistent, but lose touch with users

• Newsletters and other dissemination devices – Reach wider selection of users– Need communication both ways

• Combination of these approaches

What is a user-centered approach?

User-centered approach is based on:– Early focus on users and tasks: directly studying

cognitive, behavioral, anthropomorphic & attitudinal

characteristics – Empirical measurement: users’ reactions and

performance to scenarios, manuals, simulations & prototypes are observed, recorded and analysed

– Iterative design: when problems are found in user testing, fix them and carry out more tests

Four basic activities

There are four basic activities in Interaction Design:

– 1. Identifying needs and establishing requirements

– 2. Developing alternative designs

– 3. Building interactive versions of the designs

– 4. Evaluating designs

Some practical issues

• Who are the users?

• What are ‘needs’?

• Where do alternatives come from?

• How do you choose among alternatives?

Who are the users/stakeholders?

• Not as obvious as you think:– those who interact directly with the product– those who manage direct users– those who receive output from the product – those who make the purchasing decision – those who use competitor’s products

• Three categories of user (Eason, 1987): – primary: frequent hands-on– secondary: occasional or via someone else– tertiary: affected by its introduction, or will influence

its purchase

Who are the stakeholders?

What are the users’ capabilities?

Humans vary in many dimensions: — size of hands may affect the size and positioning of input buttons — motor abilities may affect the suitability of certain input and output devices — height if designing a physical kiosk — strength - a child’s toy requires little strength to operate, but greater strength to change batteries— disabilities(e.g. sight, hearing, dexterity)

What are ‘needs’?• Users rarely know what is possible

• Users can’t tell you what they ‘need’ to help them achieve their goals

• Instead, look at existing tasks:– their context

– what information do they require?

– who collaborates to achieve the task?

– why is the task achieved the way it is?

• Envisioned tasks:– can be rooted in existing behaviour

– can be described as future scenarios

What do we need to look out for in interface design issues?

Where do alternatives come from?

• Humans stick to what they know works• But considering alternatives is important to

‘break out of the box’• Designers are trained to consider alternatives,

software people generally are not• How do you generate alternatives?

—‘Flair and creativity’: research and synthesis —Seek inspiration: look at similar products or

look at very different products

How do you choose among alternatives?• Evaluation with users or with peers, e.g.

prototypes• Technical feasibility: some not possible• Quality thresholds: Usability goals lead to

usability criteria set early on and check regularly

—safety: how safe?—utility: which functions are superfluous?

—effectiveness: appropriate support? task coverage, information available

—efficiency: performance measurements

Testing prototypes to choose among alternatives

HCI in the software process

• Software engineering and the design process for interactive systems

• Usability engineering

• Iterative design and prototyping

• Design rationale

Lifecycle models

• Show how activities are related to each other• Lifecycle models are:

—management tools—simplified versions of reality

• Many lifecycle models exist, for example:—from software engineering: waterfall, spiral, JAD/RAD,

Microsoft, agile—from HCI: Star, usability engineering

The waterfall model

Requirementsspecification

Requirementsspecification

Architecturaldesign

Architecturaldesign

Detaileddesign

Detaileddesign

Coding andunit testingCoding andunit testing

Integrationand testingIntegrationand testing

Operation andmaintenance

Operation andmaintenance

Activities in the life cycle

Requirements specificationdesigner and customer try capture what the system is expected to provide can be expressed in natural language or more precise languages, such as a task analysis would provide

Architectural designhigh-level description of how the system will provide the services required factor system into major components of the system and how they are interrelated needs to satisfy both functional and nonfunctional requirements

Detailed designrefinement of architectural components and interrelations to identify modules to be implemented separately the refinement is governed by the nonfunctional requirements

DSDM lifecycle model

The Star lifecycle model

• Suggested by Hartson and Hix (1989)

• Important features:—Evaluation at the center of activities—No particular ordering of activities; development may start in any one—Derived from empirical studies of interface designers

The Star Model (Hartson and Hix, 1989)

Usability engineering lifecycle model• Reported by Deborah Mayhew• Important features:

– Holistic view of usability engineering– Provides links to software engineering approaches,

e.g. OOSE – Stages of identifying requirements, designing,

evaluating, prototyping– Can be scaled down for small projects– Uses a style guide to capture a set of usability goals

ISO 13407

Verification and validation

Verificationdesigning the product right

 Validationdesigning the right product

 The formality gap

validation will always rely to some extent on subjective means of proof

Management and contractual issuesdesign in commercial and legal contexts

Real-worldrequirementsand constraints The formality gap

The life cycle for interactive systems

cannot assume a linearsequence of activities

as in the waterfall model

lots of feedback!

Requirementsspecification

Requirementsspecification

Architecturaldesign

Architecturaldesign

Detaileddesign

Detaileddesign

Coding andunit testingCoding andunit testing

Integrationand testingIntegrationand testing

Operation andmaintenance

Operation andmaintenance

Usability engineering

The ultimate test of usability based on measurement of user experience

Usability engineering demands that specific usability measures be made explicit as requirements

Usability specification– usability attribute/principle– measuring concept– measuring method– now level/ worst case/ planned level/ best case

Problems– usability specification requires level of detail that may not be– possible early in design satisfying a usability specification– does not necessarily satisfy usability

part of a usability specification for a VCR

Attribute: Backward recoverability

Measuring concept: Undo an erroneous programming sequence

Measuring method: Number of explicit user actionsto undo current program

Now level: No current product allows such an undo Worst case: As many actions as it takes to

program-in mistake Planned level: A maximum of two explicit user actions Best case: One explicit cancel action

ISO usability standard 9241

adopts traditional usability categories:

• effectiveness– can you achieve what you want to?

• efficiency– can you do it without wasting effort?

• satisfaction– do you enjoy the process?

some metrics from ISO 9241

Usability Effectiveness Efficiency Satisfactionobjective measures measures measures

Suitability Percentage of Time to Rating scale for the task goals achieved complete a task for satisfaction

Appropriate for Number of power Relative efficiency Rating scale for

trained users features used compared with satisfaction with

an expert user power features

Learnability Percentage of Time to learn Rating scale forfunctions learned criterion ease of learning

Error tolerance Percentage of Time spent on Rating scale for errors corrected correcting errors error handling successfully

Iterative design and prototyping• Iterative design overcomes inherent problems of incomplete

requirements

• Prototypes– simulate or animate some features of intended system– different types of prototypes

• throw-away• incremental• evolutionary

• Management issues– time– planning– non-functional features– contracts

Techniques for prototyping

Storyboardsneed not be computer-basedcan be animated

Limited functionality simulationssome part of system functionality provided by designerstools like HyperCard are common for these Wizard of Oz technique

Warning about iterative designdesign inertia – early bad decisions stay baddiagnosing real usability problems in prototypes….

…. and not just the symptoms

Design rationale

Design rationale is information that explains why a computer system is the way it is.

Benefits of design rationale– communication throughout life cycle– reuse of design knowledge across products– enforces design discipline– presents arguments for design trade-offs– organizes potentially large design space– capturing contextual information

Design rationale (cont’d)

Types of DR:• Process-oriented

– preserves order of deliberation and decision-making

• Structure-oriented– emphasizes post hoc structuring of considered

design alternatives

• Two examples:– Issue-based information system (IBIS)– Design space analysis

Issue-based information system (IBIS)• basis for much of design rationale research

• process-oriented

• main elements:issues

– hierarchical structure with one ‘root’ issue

positions– potential resolutions of an issue

arguments– modify the relationship between positions and issues

• gIBIS is a graphical version

structure of gIBIS

Sub-issue

Issue

Sub-issue

Sub-issue

Position

Position

Argument

Argument

responds to

responds toobjects to

supports

questions

generalizes

specializes

Design space analysis

• structure-oriented

• QOC – hierarchical structure:questions (and sub-questions)

– represent major issues of a design

options– provide alternative solutions to the question

criteria – the means to assess the options in order to make a choice

• DRL – similar to QOC with a larger language and more formal semantics

the QOC notation

Question

Option

Option

Option

Criterion

Criterion

Criterion

Question … ConsequentQuestion

…

Psychological design rationale• to support task-artefact cycle in which user tasks are

affected by the systems they use

• aims to make explicit consequences of design for users

• designers identify tasks system will support

• scenarios are suggested to test task

• users are observed on system

• psychological claims of system made explicit

• negative aspects of design can be used to improve next iteration of design

A simple interaction design model

Exemplifies a user-centered design approach

SummaryFour basic activities in the design process

1. Identify needs and establish requirements2. Design potential solutions ((re)-design)3. Choose between alternatives (evaluate)4. Build the artefact

User-centered design rests on three principles1. Early focus on users and tasks2. Empirical measurement using quantifiable &

measurable usability criteria3. Iterative design

Lifecycle models show how these are related

Summary

The software engineering life cycle– distinct activities and the consequences for

interactive system design

Usability engineering– making usability measurements explicit as

requirements

Iterative design and prototyping– limited functionality simulations and animations

Design rationale– recording design knowledge– process vs. structure