Chapter five HCI

INTERACTION DESIGN AND
HCI IN THE SOFTWARE PROCESS
CHAPTER FIVE
1

Interaction design
 Interaction design is about how the artifact produced is going to affect
the way people work:
 The design of interventions
What is design?
 Design: achieving goals within constraints
 Constraint: the limitations on the design process by external factors
 Trade-off: choosing which goals or constraints can be relaxed so that others
can be met.
The golden rule of design
 Understand your material:
 Computers (limitations, capacities, tools, platforms) and
 People (psychological, social aspects, human error)2

Interaction design
To err is human
 It is the nature of humans to make mistakes and systems should be
designed:
 To reduce the likelihood of those mistakes
 To minimize the consequences when mistakes happen
The process of design
 Requirements: Through observations and interviews, the features of the
system to be designed are mapped.
 Analysis: Through various methods, the gathered requirements are
ordered to bring out key issues.
 Design: Various design guidelines help you to move from what you want
to how to do it.
 Iteration and prototyping: Try out early versions of the system with real3

Interaction design
 User focus
 Gather as much information as possible about the future users of the system.
 Terminology:
 Stakeholders: people affected directly or indirectly by a system
 Participatory design: bringing a potential user fully into the design process
 Persona: rich picture of an imaginary person who represents your core user group
 Scenarios
 Scenarios are stories for design
 The simplest design representation, but one of the most flexible and powerful.
 E.g. ‘the user intends to press the “save” button, but accidentally presses the “quit”
button so loses his work’.
 Rich stories of interaction sometimes illustrated with storyboards.
4

Interaction design
 Navigation design
 Local structure
 Much of interaction involves goal-seeking behavior, because users do not know the system
entirely.
 Therefore, the interface should always make clear:
 where you are
 what you can do
 where you are going/what will happen in terms of the interaction or state of the system.
 Icons are not self-explanatory: they should be explained!
 The different meaning of the same command in different modes should be clear.
 The system should give feedback about the effect of an action.
 Global structure- hierarchical organization
 Overall structure of an application:
 The way the various screens, pages or physical device states link to one another
 This can be done using hierarchy:
 humans tend to be better at using this structure, as long as the hierarchy does not go to
deep
 Global structure- dialog
 The pattern of non-hierarchical interaction occurring when the user performs a certain
action
5

Interaction design
 Screen design and layout
 Tools for layout
 Grouping and structure
o If things logically belong together, then we should normally visually group them
together.
 Order of groups and items: the order on the screen should follow the natural order for the
user.
 Decoration: decorations can be used to emphasize grouping.
 Alignment: the proper use of alignment can help the user to find information in lists and
columns quickly.
 White space: white space can be used to separate blocks, highlight structures etc.
 User actions and control
 For entering information, the same criteria dictate the layout.
 It is also very important that the interface gives a clear clue what to do.
 A uniform layout is helpful.
 Affordance (things may (by their shape for example) suggest what to do with them) is
sometimes helpful.
 Appropriate appearance
 The way of presenting information on screen depends on:
• The kind of information
6

Interaction design
Iteration and prototyping
 In order for prototyping methods to work, you need:
• To understand what is wrong and how to improve it
• A good starting point.
 If the design is very complex
• It is sometimes wise to start with various alternatives
• To drop them one by one during the design process.
7

HCI in the software process
 Introduction
 Software life cycle
 The activities that take place from the initial concept for a software system up
until its eventual phasing out and replacement.
 HCI aspects are relevant within all the activities of the software life cycle.
 The software life cycle
 Activities in software life cycle
 Requirements specification: capture a description of what the eventual system will be
expected to provide.
 Architectural design: how does the system provide the services expected from it.
 The system is decomposed into components.
 Detailed design: a refinement of the component description provided by the
architectural design, made for each component separately.
 Coding and unit testing: implementing the detailed design in an executable
programming language and testing the different components.
 Integration and testing: integrating the different components into a complete system
and testing it as a whole.
 Maintenance: all the work on the system after the system is released.8

9
The activities in the waterfall model of the software life cycle
Requirements
specification
Architectural
design
Detailed
design
Coding and
unit testing
Integration
and testing
Operation and
maintenance

The software life cycle
 Validation and verification
 Verification (designing the product right) will most often occur within a
single life-cycle activity or between two adjacent activities.
 Validation of a design (designing the right product) demonstrates that
within the various activities the customer’s requirements are satisfied.
 Management and contractual issues
 In managing the development process
 the temporal relationship between the various activities is more
important
 As are the intermediate deliverables which represent the technical
content
 As the designer must demonstrate to the customer that progress is
being made
 The technical perspective of the life cycle is described in stages of
activity10

The software life cycle
 Interactive systems and the software life cycle
 The life cycle for development described above presents the process of
design in a somewhat pipeline order.
 In reality, the actual process is iterative:
 Work in one design activity affects work in any other activity both before
or after it in the life cycle.
 All of the requirements for an interactive system cannot be determined from
the start.
 During the design process, the system is made more usable by having the
potential user test the prototypes and observe his behavior.
 In order to do this, clear understanding of human task performance and
cognitive processes is very important.
11

Usability engineering
 Usability
 The degree to which a given piece of software assists the person sitting at the
keyboard to accomplish a task.
 The emphasis for usability engineering is in knowing exactly what criteria will be
used to judge a product for its usability.
 Various attribute of the system are suggested as gauges for testing the usability.
 For each attribute, six items are defined to form the usability specification of that
attribute:
 Measuring concept: makes the abstract attribute more concrete by describing it
in terms of the actual product.
 Measuring method: states how the attribute will be measured.
 Now level: indicates the value for the measurement with the existing system.
 Worst case: the lowest acceptable measurement for the task.
 Planned level: the target for the design.
 Best case: the level which is agreed to be the best possible measurement given
the current state of development tools and technology.12

Usability engineering
 Problems with usability engineering
 The major feature of usability engineering is the assertion of explicit
usability metrics early on in the design process
 used to judge a system once it is delivered
 The problem with usability metrics is that they rely on measurements of
very specific user actions in very specific situations.
 At early stages of design, the designers do not yet have the information
to set goals for measured observations.
 Another problem is that usability engineering provides a means of
satisfying usability specifications and not necessarily usability.
13

Iterative design and prototyping
 Iterative design: a purposeful design process which tries to overcome the
inherent problems of incomplete requirement specification by cycling through
several designs
 Incrementally improving upon the final product with each pass
 On the technical side, this is described by the use of prototypes
 There are 3 main approaches of prototyping:
 Throw-away: the knowledge gained from the prototype is used in the final
design, but the prototype is discarded.
 Incremental: the final product is released as a series of components that have
been prototyped separately.
 Evolutionary: the prototype is not discarded but serves as a basis for the next
iteration of the design.
 Prototypes differ according to the amount of functionality and performance they
provide relative to the final product.
 The importance lies in its projected realism, since they are tested on real users.
14

Iterative design and prototyping
 Techniques for prototyping
 Storyboards: a graphical depiction of the outward appearance of
the intended system, without any accompanying system
functionality.
 Limited functionality simulations
 A designer can rapidly build graphical and textual interaction objects, and
 Attach some behavior to those objects, which mimics the system’s
functionality.
 High-level programming support
 High-level programming languages allow the programmer to abstract
away from:
 The hardware specifics
 Thinking terms that are closer to the way the input and output devices
are perceived as interaction devices.
 This technique can also be provided by a user interface management
15

Design Rationale
 DR is the information that explains why a computer system is the way it is
 including its structural and functional description.
 The benefits of DR:
 Provides a communication mechanism among the members of the design
team.
 Reuse of design knowledge across products
 Enforces design discipline
 Presents arguments for design trade-offs
 Organizes potentially large design space
 Capturing contextual information
16

Design Rationale
 Process-oriented design rationale
 DR is often represented using the IBIS (issue-based information system), in
which a hierarchical process oriented structure is used:
 A root issue identifies the main problem
 Various descendent positions are put forth as potential solutions.
 Design space analysis
 In this representation, the design space is initially structured by a set of
questions representing the major issues of the design.
 Options provide alternative solutions to the question.
 Options can evoke criteria and new questions
 Therefore the entire representation can also be hierarchically visualized in a
tree-graph.
17

Design Rationale
 Psychological design rationale
 The purpose of PDR is to design the natural task-artifact cycle of design
activity.
 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 design18

Chapter five HCI

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