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11© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Gebruikersaspecten van software systemen
User Aspects of Software Systems
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22© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
User Aspects of Software SystemsUser Aspects of Software Systems
Books: • [1] “User-Centered Website Development. A Human-
Computer Interaction Approach”, D.D. McCracken, R.J. Wolfe, Pearson Prentice Hall, 2004.
• [2] “Model-Based Design and Evaluation of Interactive Applications”, F. Paternò, Springer, 2000.
• [3] “Graphical User Interface Design and Evaluation”, • Redmon-Pyle and Moore, Prentice-Hall, 1995
• WebSite: via elvas or via wise.vub.ac.be
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33© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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What is this course about?
• How to make a good (= usable) user interface for an interactive application
• Why are usable user interfaces important?
– Nearly all applications have a user interface
– Bad interfaces are frustrating for the user and will influence the productivity
– Competitors may have better systems
• Good user interface are hardly noticed, bad ones are!
• It is easier to make a bad interface than a good one.
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44© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Content (1)
1. Introduction – Usability: Illustrating example– HCI overview– User-Centered Development Methodology
2. Capabilities of the Human Being
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55© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Content (2)3. The User Interface Design Process
3.1 The Users and their Usability Requirements3.2 Task Analysis & Task Modeling3.3 User Object Modeling3.4 The Style Guide3.5 Design
• Task-Driven Design• Visual Organization• Use of Color• Typography • Multimedia
3.6 Prototyping3.7 Evaluation
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66© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Content (3)4. Accessibility5. Localization6. Model-Based Approaches for UI design
GOMSNorman’s cycleTask analysis methodsUANPetri NetsUML
More details on the website
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77© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Format of the Course
• Chapter 6 – Self-study
• Rest (Methodology)– During the lessons
• Project in groups
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88© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Good Design is as easy as 1-2-3
1. Learn the principlesThey are simpler than you might think
2. Recognize when you are not using themPut into words - name the problems
3. Apply the principles you will be amazed
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99© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
User Aspects of Software SystemsUser Aspects of Software Systems
Chapter 1 Introduction
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1010© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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1. Introduction
Content
• Usability: Illustrating example
• The history and goals of Human-Computer Interaction
• The methodology of User-Centered Development
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1111© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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1.1 Illustrating Example
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1212© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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It doesn’t have to be that way
• You can design user interfaces that– Are pleasant and convenient for your users– Let them accomplish their goals
• The key: think about your users– Learn about them– Watch them work, in their workplace– Interview them, also in their workplace
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1313© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Benefits of Usable User Interfaces
• Gaining a competitive edge
• Reducing development and maintenance costs
• Improving productivity
• Lowering support costs
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1414© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Reducing development and maintenance costs
• Learn about users first, and you will avoid– Implementing features users don’t want– Creating features that are annoying or
inefficient– High cost of making changes late in the
development cycle
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1515© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Improving productivity
• Productivity means employees become more efficient because the system supports their tasks in an easy way.
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1616© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Lower support costs
• Calls to customer support are very expensive for the vendor: estimates range from €12 to €250 per call
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1717© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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1.2 What is HCI?“Human Computer Interaction is 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.”
– As defined by the Special Interest Group on Human-Computer Interaction (SIGCHI) of the Association for Computing Machinery (ACM)
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1818© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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A major shift
• 50 years ago the cost of a computer would pay the salaries of 200 programmers for a year
• Today the salary of one programmer for a year will buy 200 computers—each vastly more powerful than the early machines
• Late 70’s: smaller and cheaper computers (PC’s) used by non-computer experts– Now the goal is to make computers easy to use, to
save people time
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1919© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Examples of interactive computing systems
• Single PC - capable of displaying web pages
• Embedded devices, for example in cars and in cell phones
• Handheld Global Positioning Systems for outdoor activities
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2020© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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1.3 Goals of HCITo develop or improve the• Safety• Utility• Effectiveness• Efficiency• Usability• Appeal
. . . of systems that include computers
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2121© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Safety
• Safety of Users—think of– Air traffic control– Hospital intensive care
• Safety of Data—think of– Protection of files from tampering– Privacy and security
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2222© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Utility and effectiveness• Utility: what services a system provides
e.g. Ability to print documents
• Effectiveness: user’s ability to achieve goals, e.g.
– How to enter the desired information – How to print a report
• Utility and effectiveness are distinct– A system might provide all necessary services, but if
users can’t find the services items, the system lacks effectiveness
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2323© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Efficiency
• A measure of how quickly users can accomplish their goals or finish their work using the system
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Usability
• Definitions – “a measure of the ease with which a system can
be learned and used, its safety, effectiveness and efficiency, and attitude of its users towards it” (Preece et al., 1994)
– “the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use” (ISO 9241-11)
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2525© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Usability (2)
• Ease of learning !
• Ease of use !
• Appeal/ attitude !– How well users like the system– First impressions – Long-term satisfaction
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26© Prof. Dr. O. De Troyer, 1999 2626© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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• How can we measure usability?• How can we develop a system to ensure
usability?
Paradigms– Usually based on new technology
E.g. WIMP interface
Principles– Independent of technology
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27© Prof. Dr. O. De Troyer, 1999 2727© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Principles to support usability
• Learnability– The ease with which new users can use the
system effectively
• Flexibility– The multiplicity of ways the user and the system
exchange information
• Effectiveness– the level of support provided to the user to
achieve successfully its goals
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28© Prof. Dr. O. De Troyer, 1999 2828© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Learnability
Principles affecting learnability: – Predictability: to be able to predict the result of an interaction– Feedback: the system provides feedback about the effect of the
interaction– Familiarity: correlation between the user’s existing knowledge
and the knowledge required to use the interaction– Generalization: e.g. drawing rectangle will be the same as
drawing square; close/open window will be the same as in other MS word application
– Consistency: in naming, color use, command invocation, …
• Advantages• reduces training time and costs• enable more flexible staffing practices (staff become effective
more quickly)
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29© Prof. Dr. O. De Troyer, 1999 2929© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Flexibility (1)
• Examples:– Input/output in different forms
• Inches/cm, fixed point/decimal, % or fixed part, …
– Input may be output and vice versa:• Draw line, out: coordinates• Give coordinates, out: draw line
– Order of tasks is not fixed
• System driven interaction hinders flexibility, user-driven interaction favors it
• Multi-treading allows to support more than one task at the time
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30© Prof. Dr. O. De Troyer, 1999 3030© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Flexibility (2)
Related:• Customization:
– Adaptability: user can adapt the user interface– Adaptivity: The user interface can be adapted by the
system – Personalization: user interface is tailored towards the
individual user
• Advantages– allows reorganization of tasks and business
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31© Prof. Dr. O. De Troyer, 1999 3131© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Effectiveness
• Always for a specified range of tasks and group of users in a particular environment.
• Principles affecting effectiveness:– Ability to observe the internal state of the system– Ability to take corrective actions once an error has been
recognized– Response time – Task completeness: are all user tasks supported by the system?– Task adequacy: match of the task as understood by the user and
supported by the system
• Advantages:– higher productivity
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32© Prof. Dr. O. De Troyer, 1999 3232© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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1.4 User-Centered Development Methodology
• Traditional software engineering methods arose in 1960s and 1970s– Systems were not highly interactive– End-user were computer specialists Issues concerning end-user and usability were not at
all important user interface design not considered explicitly
• Now:– Most end-users are not computer specialists– Usability vital for success
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33© Prof. Dr. O. De Troyer, 1999 3333© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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• Traditional System-Centered design:– Emphasis on the functionality,
– UI is added at the end
– Emphasis on correct software rather than on ease of use
– User has to adapt himself to the system
• Things are changing: User-Centered design – UI more important
– Emphasis on end-users’ tasks,
– Early end-user participation: in analysis and design
– Evaluation by end-users
– Consequences:
• more work for UI-designer and UI-programmer
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34© Prof. Dr. O. De Troyer, 1999 3434© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Summary: User Centered Development
• User-centric, not data-centric– Involves users in the design process– Usability can be quantified and measured
• Highly Iterative– Involves testing and revision
• Interdisciplinary, building on a dozen different disciplines
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35© Prof. Dr. O. De Troyer, 1999 3535© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Fields that HCI builds on (1)
• Computer Science– Implementation of software
• Engineering– Faster, cheaper equipment
• Ergonomics– Design for human factors
• Graphic design– Visual communication
• Technical writing– Textual communication
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36© Prof. Dr. O. De Troyer, 1999 3636© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004
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Fields that HCI builds on (2)
• Linguistics, artificial intelligence– Speech recognition, natural language processing
• Cognitive psychology– Perception, memory, mental models
• Sociology– How people interact in groups
• Anthropology– Study of people in their work settings