Gebruikersaspecten van software systemen User Aspects of Software Systems

11© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004

User Aspects of Software SystemsUser Aspects of Software Systems

Gebruikersaspecten van software systemen

User 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



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.



Content (1)

1. Introduction – Usability: Illustrating example– HCI overview– User-Centered Development Methodology

2. Capabilities of the Human Being



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



Content (3)4. Accessibility5. Localization6. Model-Based Approaches for UI design

GOMSNorman’s cycleTask analysis methodsUANPetri NetsUML

More details on the website



Format of the Course

• Chapter 6 – Self-study

• Rest (Methodology)– During the lessons

• Project in groups



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



Chapter 1 Introduction



1. Introduction

Content

• Usability: Illustrating example

• The history and goals of Human-Computer Interaction

• The methodology of User-Centered Development



1.1 Illustrating Example



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



Benefits of Usable User Interfaces

• Gaining a competitive edge

• Reducing development and maintenance costs

• Improving productivity

• Lowering support costs



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



Improving productivity

• Productivity means employees become more efficient because the system supports their tasks in an easy way.



Lower support costs

• Calls to customer support are very expensive for the vendor: estimates range from €12 to €250 per call



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)



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



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



1.3 Goals of HCITo develop or improve the• Safety• Utility• Effectiveness• Efficiency• Usability• Appeal

. . . of systems that include computers



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



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



Efficiency

• A measure of how quickly users can accomplish their goals or finish their work using the system



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)



Usability (2)

• Ease of learning !

• Ease of use !

• Appeal/ attitude !– How well users like the system– First impressions – Long-term satisfaction

26© Prof. Dr. O. De Troyer, 1999 2626© Prof. Dr. O. De Troyer, 2004© Prof. Dr. O. De Troyer, 2004


• 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



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



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)



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



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



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



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



• 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



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



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



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

Gebruikersaspecten van software systemen User Aspects of Software Systems

Documents

Transcript of Gebruikersaspecten van software systemen User Aspects of Software Systems