usability requirements
DESCRIPTION
Week 5 lecture for im2044 2012-2013TRANSCRIPT
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IM2044 – Week 6: LectureDr. Andres Baravalle
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Interaction design
• The next slides are based on the companion slides for the textbook
• By the end of this week, you should have studied all chapters of the textbook up to chapter 10
• Today we will covering chapters 9-10.
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Overview
• What is Interaction Design?– Importance of involving users– Degrees of user involvement– What is a user-centered approach?
• Some practical issues:– Who are the users?– What are ‘needs’?– Where do alternatives come from?– How do you choose among
alternatives?
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What is 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
• Four approaches: user-centered design, activity-centered design, systems design, and genius design
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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
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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• Dissemination devices, as newsletters
– Reach wider selection of users– Need communication both ways
• User involvement after product is released• Combination of these approaches
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What is a user-centered approach?• User-centered approach is based on:
– Early focus on users and tasks: directly studying user characteristics (cognitive, behavioural, anthropomorphic & attitudinal)
– 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
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Interaction design activities
• Establishing requirements
• Designing alternatives
• Prototyping
• Evaluating
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A simple interaction design lifecycle model• Who are the users?
• What do we mean by ‘needs’?
• How to generate alternatives
• How to choose among alternatives
• How to integrate interaction design activities with other models?
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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
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Who are the stakeholders?
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Check-out operators
CustomersManagers and owners
• Suppliers• Local shop owners
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What do we mean by ‘needs’?• Users rarely know what is possible• Users (typically) 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
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How to generate alternatives
• Humans stick to what they know works– Considering alternatives is important to ‘break out of
the box’
• Designers are trained to consider alternatives, software developers 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
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How to 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
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How to choose among alternatives
Test the alternatives!
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How to integrate interaction design in other models?• Agile software development is one option:
– Have development and design running in separate tracks
– Maintain a coherent vision of the interface architecture
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Software requirements: what, how and why
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• What:1. Understand as much as possible about users, task, context2. Produce a stable set of requirements
• How:Data gathering activitiesData analysis activitiesExpression as ‘requirements’All of this is iterative
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Software requirements: what, how and why (2)
•Why:Requirements definition: the stage where failure occurs most commonly
•Getting requirements right is crucial
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Volere shell
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Volere requirements template
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Establishing requirements
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• What do users want? What do users ‘need’? • Requirements need clarification, refinement,
completion, re-scoping• Input: requirements document (maybe) • Output: stable requirements
• Why ‘establish’?• Requirements arise from understanding users’
needs• Requirements can be justified & related to data
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Different kinds of requirements• Functional:
—What the system should do—Historically the main focus of requirements activities
• (Non-functional: memory size, response time...)• Data:
—What kinds of data need to be stored?—How will they be stored (e.g. database)?
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Different kinds of requirements (2)Environment or context of use:
— Physical: dusty? noisy? vibration? light? heat? humidity? …. (e.g. OMS insects, ATM)— Social: sharing of files, of displays, in
paper, across great distances, work individually, privacy for clients— Organisational: hierarchy, IT department’s
attitude and remit, user support, communications structure and infrastructure, availability of training
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An extreme example
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Different kinds of requirements (3)
• Users: Who are they?— Characteristics: ability, background, attitude to computers— System use: novice, expert, casual, frequent— Novice: step-by-step (prompted), constrained, clear information— Expert: flexibility, access/power— Frequent: short cuts— Casual/infrequent: clear instructions, e.g. menu paths
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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)
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Kinds of requirements
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• What factors (environmental, user, usability) would affect the following systems?• Self-service filling and payment system
for a petrol (gas) station• On-board ship data analysis system for
geologists searching for oil• Fashion clothes website
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Personas (stereotypes)
• Capture user characteristics– Not real people, but synthesised from real
user characteristics– Should not be idealised– Bring them to life with a name, characteristics,
goals, personal background
• Develop multiple personas
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Personas
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Data gathering for requirements
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Interviews:— Props, e.g. sample scenarios of use,
prototypes, can be used in interviews— Good for exploring issues — But are time consuming and may be
infeasible to visit everyoneFocus groups:
— Group interviews— Good at gaining a consensus view and/or highlighting areas of conflict— But can be dominated by individuals
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Data gathering for requirements (2)
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Questionnaires:— Often used in conjunction with other
techniques— Can give quantitative or qualitative data— Good for answering specific questions from
a large, dispersed group of people
Researching similar products:— Good for prompting requirements
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Data gathering for requirements (3)
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Direct observation:— Gain insights into stakeholders’ tasks — Good for understanding the nature and
context of the tasks— But, it requires time and commitment
from a member of the design team, and it can result in a huge amount of data
Indirect observation:— Not often used in requirements activity— Good for logging current tasks
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Data gathering for requirements (4)
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Studying documentation: — Procedures and rules are often written
down in manuals — Good source of data about the steps
involved in an activity, and any
regulations governing a task— Not to be used in isolation— Good for understanding legislation, and
getting background information— No stakeholder time, which is a limiting
factor on the other techniques
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Problems with data gathering (1)• Identifying and involving stakeholders:
users, managers, developers, customer reps?, union reps?, shareholders?
• Involving stakeholders: workshops, interviews, workplace studies, co-opt stakeholders onto the development team
• Getting ‘real’ users, not managers:traditionally a problem in software engineering
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Problems with data gathering (2)• Requirements management: version control, ownership• Communication between parties:
– Within development team– With customer/user– Between users… different parts of an organisation
use different terminology• Domain knowledge distributed and implicit:
– Difficult to dig up and understand– Knowledge articulation: how do you walk?
• Availability of key people
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Problems with data gathering (3)•Political problems within the organisation•Dominance of certain stakeholders•Economic and business environment
changes•Balancing functional and usability
demands
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Some basic guidelines
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•Focus on identifying the stakeholders’
needs
• Involve all the stakeholder groups
• Involve more than one representative
from each stakeholder group
•Use a combination of data gathering
techniques
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Some basic guidelines (2)
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• Support the process with props such as
prototypes and task descriptions
• Run a pilot session
• You will need to compromise on the data you
collect and the analysis to be done, but before
you can make sensible compromises, you need
to know what you’d really like
• Consider carefully how to record the data
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Data interpretation and analysis
•Start soon after data gathering session• Initial interpretation before deeper
analysis•Different approaches emphasize different
elements e.g. class diagrams for object-oriented systems, entity-relationship diagrams for data intensive systems
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Task descriptions
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• Scenarios― An informal narrative story, simple, ‘natural’,
personal, not generalisable
• Use cases— Assume interaction with a system— Assume detailed understanding of the
interaction
• Essential use cases— Abstract away from the details— Does not have the same assumptions as use
cases
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Task analysis• Task descriptions are often used to envision new
systems or devices• Task analysis is used mainly to investigate an existing
situation• It is important not to focus on superficial activities
– What are people trying to achieve? – Why are they trying to achieve it?– How are they going about it?
• Many techniques, the most popular is Hierarchical Task Analysis (HTA)
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Hierarchical Task Analysis
• Involves breaking a task down into subtasks, then sub-sub-tasks and so on. These are grouped as plans which specify how the tasks might be performed in practice
• HTA focuses on physical and observable actions, and includes looking at actions not related to software or an interaction device
• Start with a user goal which is examined and the main tasks for achieving it are identified
• Tasks are sub-divided into sub-tasks
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Example Hierarchical Task Analysis
0. In order to buy a DVD1. locate DVD2. add DVD to shopping basket3. enter payment details4. complete address5. confirm order
plan 0: If regular user do 1-2-5. If new user do 1-2-3-4-5.
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Example Hierarchical Task Analysis (graphical)
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Hierarchical Task Analysis (2)
• More in the tutorial
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