Chapter 29 Interaction design Chapter 29 is available

Chapter 29 - Interaction design Chapter 29 is available online: http: //www. cs. st-andrews. ac. uk/~ifs/Books/SE 9/Web. Chapters/PDF/Ch_29%20 Interaction_design. pdf Chapter 29 Interaction design 1

Topics covered ² Design issues ² The user interface design process ² User analysis ² User interface prototyping ² Interface evaluation Chapter 29 Interaction design 2

The user interface ² User interfaces should be designed to match the skills, experience and expectations of its anticipated users. ² System users often judge a system by its interface rather than its functionality. ² A poorly designed interface can cause a user to make catastrophic errors. ² Poor user interface design is the reason why so many software systems are never used. Chapter 29 Interaction design 3

Activity Take a look at these images for 15 seconds. . Chapter 29 Interaction design 4

Activity On a piece of paper write down what you remember. How many items did you remember? Average = 7+/-2 Chapter 29 Interaction design 5

Human factors in interface design ² Limited short-term memory § People can instantaneously remember about 7 items of information. If you present more than this, they are more liable to make mistakes. ² People make mistakes § When people make mistakes and systems go wrong, inappropriate alarms and messages can increase stress and hence the likelihood of more mistakes. ² People are different § People have a wide range of physical capabilities. Designers should not just design for their own capabilities. ² People have different interaction preferences § Some like pictures, some like text. Chapter 29 Interaction design 6

UI design principles ² UI design must take account of the needs, experience and capabilities of the system users. ² Designers should be aware of people’s physical and mental limitations (e. g. limited short-term memory) and should recognise that people make mistakes. ² UI design principles underlie interface designs although not all principles are applicable to all designs. Chapter 29 Interaction design 7

UI design principles ² User familiarity § The interface should be based on user-oriented terms and concepts rather than computer concepts. For example, an office system should use concepts such as letters, documents, folders etc. rather than directories, file identifiers, etc. ² Consistency § The system should display an appropriate level of consistency. Commands and menus should have the same format, command punctuation should be similar, etc. ² Minimal surprise § If a command operates in a known way, the user should be able to predict the operation of comparable commands Chapter 29 Interaction design 8

UI design principles, cont. ² Recoverability § The system should provide some resilience to user errors and allow the user to recover from errors. This might include an undo facility, confirmation of destructive actions, 'soft' deletes, etc. ² User guidance § Some user guidance such as help systems, on-line manuals, etc. should be supplied ² User diversity § Interaction facilities for different types of user should be supported. For example, some users have seeing difficulties and so larger text should be available Chapter 29 Interaction design 9

Design issues in UIs ² Two problems must be addressed in interactive systems design § How should information from the user be provided to the computer system? § How should information from the computer system be presented Information Presentation to the user? ² User interaction and information User Interaction Style presentation may be integrated through a coherent framework such as a user interface metaphor. Chapter 29 Interaction design 10

Interaction styles ² Direct manipulation ² Menu selection ² Form fill-in ² Command language ² Natural language Chapter 29 Interaction design 11

Interaction Styles: Direct Manipulation Chapter 29 Interaction design 12

Interaction Styles: Menu Selection Chapter 29 Interaction design 13

Interaction Styles: Form Fill-in Chapter 29 Interaction design 14

Interaction Styles: Command Language Chapter 29 Interaction design 15

Interaction Styles: Natural Language Writing commands in natural language, such as ‘print the file named abc. doc’ Vocal input (e. g. Dragon Naturally Speaking) Chapter 29 Interaction design 16

Interaction styles Chapter 29 Interaction design 17

EX. LIBSYS interaction ² Document search § Users need to be able to use the search facilities to find the documents that they need. ² Document request § Users request that a document be delivered to their machine or to a server for printing. Chapter 29 Interaction design 18

Web-based interfaces ² Many web-based systems have interfaces based on web forms. ² Form field can be menus, free text input, radio buttons, etc. ² In the LIBSYS example, users make a choice of where to search from a menu and type the search phrase into a free text field. Chapter 29 Interaction design 19

EX. LIBSYS search form Chapter 29 Interaction design 20

Information presentation ² Information presentation is concerned with presenting system information to system users (e. g. Style, Colour and Error messages) ² The information may be presented directly (e. g. text in a word processor) or may be transformed in some way for presentation (e. g. in some graphical form). ² The Model-View-Controller approach is a way of supporting multiple presentations of data. Chapter 29 Interaction design 21

Information presentation Chapter 29 Interaction design 22

Information presentation ² Static information § Initialised at the beginning of a session. It does not change during the session. § May be either numeric or textual. ² Dynamic information § Changes during a session and the changes must be communicated to the system user. § May be either numeric or textual. Chapter 29 Interaction design 23

Interface Design: Information Styles Alternative information presentations Chapter 29 Interaction design 24

Analogue or digital presentation? ² Digital presentation § Compact - takes up little screen space; § Precise values can be communicated. ² Analogue presentation § Easier to get an 'at a glance' impression of a value; § Possible to show relative values; § Easier to see exceptional data values. Chapter 29 Interaction design 25

Interface Design: Information Styles Presentation methods Chapter 29 Interaction design 26

Interface Design: Information Styles Displaying relative values Chapter 29 Interaction design 27

Interface Design: Information Styles Data visualisation ² Concerned with techniques for displaying large amounts of information. ² Visualisation can reveal relationships between entities and trends in the data. ² Possible data visualisations are: § Weather information collected from a number of sources; § The state of a telephone network as a linked set of nodes; § Chemical plant visualised by showing pressures and temperatures in a linked set of tanks and pipes; § A model of a molecule displayed in 3 dimensions; § Web pages displayed as a hyperbolic tree. Chapter 29 Interaction design 28

Interface Design: Colour displays ² Colour adds an extra dimension to an interface and can help the user understand complex information structures. ² Colour can be used to highlight exceptional events. ² Common mistakes in the use of colour in interface design include: § The use of colour to communicate meaning; § The over-use of colour in the display. Chapter 29 Interaction design 29

Interface Design: Colour displays What is the problem with this page? Chapter 29 Interaction design 30

Interface Design: Colour use guidelines ² Limit the number of colours used and be conservative in their use. ² Use colour change to show a change in system status. ² Use colour coding to support the task that users are trying to perform. ² Use colour coding in a thoughtful and consistent way. ² Be careful about colour pairings. Chapter 29 Interaction design 31

Interface Design: Error messages ² Error message design is critically important. Poor error messages can mean that a user rejects rather than accepts a system. ² Messages should be polite, concise, consistent and constructive. ² The background and experience of users should be the determining factor in message design. Chapter 29 Interaction design 32

Design factors in message wording Chapter 29 Interaction design 33

Interface Design: User error ² Assume that a nurse misspells the name of a patient whose records he is trying to retrieve. Chapter 29 Interaction design 34

Interface Design: Good and bad message design Chapter 29 Interaction design 35

The UI design process ² UI design is an iterative process involving close liaisons between users and designers. ² The 3 core activities in this process are: § User analysis. Understand what the users will do with the system; § System prototyping. Develop a series of prototypes for experiment; § Interface evaluation. Experiment with these prototypes with users. Chapter 29 Interaction design 36

UI design process: User analysis ² If you don’t understand what the users want to do with a system, you have no realistic prospect of designing an effective interface. ² User analyses have to be described in terms that users and other designers can understand. ² Scenarios where you describe typical episodes of use, are one way of describing these analyses. Chapter 29 Interaction design 37

UI design process : User interaction scenario Jane is a student of Religious Studies and is working on an essay on Indian architecture and how it has been influenced by religious practices. To help her understand this, she would like to access some pictures of details on notable buildings but can’t find anything in her local library. She approaches the subject librarian to discuss her needs and he suggests some search terms that might be used. He also suggests some libraries in New Delhi and London that might have this material so they log on to the library catalogues and do some searching using these terms. They find some source material and place a request for photocopies of the pictures with architectural detail to be posted directly to Jane. Chapter 29 Interaction design 38

UI design process : Requirements from the scenario ² Users may not be aware of appropriate search terms so need a way of helping them choose terms. ² Users have to be able to select collections to search. ² Users need to be able to carry out searches and request copies of relevant material. Chapter 29 Interaction design 39

UI design process : User interface prototyping ² The aim of prototyping is to allow users to gain direct experience with the interface. ² Without such direct experience, it is impossible to judge the usability of an interface. ² Prototyping may be a two-stage process: § Early in the process, paper prototypes may be used; § The design is then refined and increasingly sophisticated automated prototypes are then developed. Chapter 29 Interaction design 40

UI design process : Paper prototyping ² Work through scenarios using sketches of the interface. ² Use a storyboard to present a series of interactions with the system. ² Paper prototyping is an effective way of getting user reactions to a design proposal. Chapter 29 Interaction design 41

UI design process : User interface evaluation ² Some evaluation of a user interface design should be carried out to assess its usability. ² Full scale evaluation is very expensive and impractical for most systems. ² Ideally, an interface should be evaluated against a usability specification. However, it is rare for such specifications to be produced. Chapter 29 Interaction design 42

Usability attributes Chapter 29 Interaction design 43

Key points ² User interface design principles should help guide the design of user interfaces. ² Interaction styles include direct manipulation, menu systems form fill-in, command languages and natural language. ² Graphical displays should be used to present trends and approximate values. Digital displays when precision is required. ² Colour should be used sparingly and consistently. Chapter 29 Interaction design 44

Key points ² The user interface design process involves user analysis, system prototyping and prototype evaluation. ² The aim of user analysis is to sensitise designers to the ways in which users actually work. ² UI prototyping should be a staged process with early paper prototypes used as a basis for automated prototypes of the interface. ² The goals of UI evaluation are to obtain feedback on how to improve the interface design and to assess if the interface meets its usability requirements. Chapter 29 Interaction design 45