User Interface Design and Ergonomics - National Open University of ...

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• Encourage menu & forms style, rather than richer direct manipulation style • May be used inappropriately Widget reuse is beneficial in two ways, actually. First are the conventional software engineering benefits of reusing code, like shorter development time and greater reliability. A widget encapsulates a lot of effort that somebody else has already put in. Second are usability benefits. Widget reuse increases consistency among the applications on a platform. It also (potentially) represents usability effort that its designers have put into it. A scrollbar’s affordances and behavior have been carefully designed, and hopefully evaluated. By reusing the scrollbar widget, you don’t have to do that work yourself. One problem with widgets is that they constrain your thinking. If you try to design an interface using a GUI builder – with a palette limited to standard widgets – you may produce a clunkier, more complex interface than you would if you sat down with paper and pencil and allowed yourself to think freely. A related problem is that most widget sets consist mostly of form-style widgets: text fields, labels, checkboxes – which leads a designer to think in terms of menu/form style interfaces. There are few widgets that support direct visual representations of application objects, because those representations are so application-dependent. So if you think too much in terms of widgets, you may miss the possibilities of direct manipulation. Finally, widgets can be abused, applied to UI problems for which they are not suited. An example is when a scrollbar is used for selection, rather than scrolling. Widgets generally combine a view and a controller into a single tightly-coupled object. For the widget’s model, however, there are two common approaches. One is to fuse the model into the widget as well, making it a little MVC complex. With this embedded model approach, application data must be copied into the widget to initialize it. When the user interacts with the widget, the user’s changes or selections must be copied back out. The other alternative is to leave the model separate from the widget, with a well-defined interface that the application can implement. Embedded models are usually easier for the developer to understand and use for simple interfaces, but suffer from serious scaling problems. For example, suppose you want to use a table widget to show the contents of a database. If the table widget had an embedded model, you would have to fetch the entire database and load it into the table widget, which may be prohibitively slow and memoryintensive. Furthermore, most of this is wasted work, since the user can only see a few rows of the table at a time. With a well-designed linked model, the table widget will only request as much of the data as it needs to display. The linked model idea is also called data binding. Generally, every user interface consists of the following:- • Components (View hierarchy) • Stroke drawing • Pixel model 126
• Input handling • Widgets Every modern GUI toolkit provides these pieces in some form. Microsoft Windows, for example, has widgets (e.g., buttons, menus, text boxes), a view hierarchy (consisting of windows and child windows), a stroke drawing package (GDI), pixel representations (called bitmaps), and input handling (messages sent to a window procedure). User interface toolkits are often built on top of other toolkits, sometimes for portability or compatibility across platforms, and sometimes to add more powerful features, like a richer stroke drawing model or different widgets. X Windows demonstrates this layering technique. The view hierarchy, stroke drawing, and input handling are provided by a low-level toolkit called XLib. But XLib does not provide widgets, so several toolkits are layered on top of XLib to add that functionality: Athena widgets and Motif, among others. More recent X-based toolkits (GTK+ and Qt) not only add widgets to XLib, but also hide XLib’s view hierarchy, stroke drawing, and input handling with newer, more powerful models, although these models are implemented internally by calls to XLib. Here is what the layering looks like for some common Java user interface toolkits. AWT (Abstract Window Toolkit, usually pronounced like “ought”) was the first Java toolkit. Although its widget set is rarely used today, AWT continues to provide drawing and input handling to more recent Java toolkits. Swing is the second-generation Java toolkit, which appeared in the Java API starting in Java 1.2. Swing adds a new view hierarchy (JComponent) derived from AWT’s view hierarchy (Component and Container). It also replaces AWT’s widget set with new widgets that use the new view hierarchy. subArctic was a research toolkit developed at Georgia Tech. Like Swing, subArctic relies on AWT for drawing and input handling, but provides its own widgets and views. Not shown in the picture is SWT, IBM’s Standard Widget Toolkit. (Usually pronounced “swit”. Confusingly, the W in SWT means something different from the W in AWT.) Like AWT, SWT is implemented directly on top of the native toolkits. It provides different interfaces for widgets, views, drawing, and input handling. Cross-platform toolkits face a special issue: should the native widgets of each platform be reused by the toolkit? One reason to do so is to preserve consistency with other applications on the same platform, so that applications written for the cross-platform toolkit look and feel like native applications. This is what we’ve been calling external consistency. 127
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] NATIONAL OPEN UNIVERSITY OF NIGER
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National Open University of Nigeria
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Summary ...........................
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UNIT 3 - GRAPHICAL USER INTERFACE (
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Assignments File Tutor-Marked Assig
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2 DESIGN and DESIGNING GOOD USER IN
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need both the study unit you are wo
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CIT 711: USER INTERFACE DESIGN AND
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UNIT 1 FUNDAMENTALS OF USER INTERFA
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3.3 TYPES OF USER INTERFACES Curren
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3.5 USER INTERFACE MODALITIES AND M
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Table of Contents 1.0 Introduction
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3.1.1 DESIGNING A GOOD USER INTERFA
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widgets properly is to read and und
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Figure 1:- Showing that alignment o
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6.0 TUTOR MARKED ASSIGNMENT a. How
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A graphical user interface is a typ
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Operating System. It is easy for a
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A list of items from which to selec
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collaborative work. For example, sc
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MODULE 1 UNIT 4 HUMAN COMPUTER INTE
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3.3 DIFFERNCES WITH RELATED FIELDS
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window blinds to automobile braking
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Wickens, Christopher D., John D. Le
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The International Ergonomics Associ
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approach, the Gilbreths reduced the
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3.6 BENEFITS OF ERGONOMICS The thre
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Another key to reducing lumbar disc
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MODULE 2 - USER INTERFACE DESIGN TE
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methods include inspection methods,
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Determine time of each operation (b
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unable to understand new informatio
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M cones, or, misleadingly, green co
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Motor skill which is a learned seri
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MODULE 2 UNIT 2 UNDERSTANDING USERS
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The users of a system must be ident
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This example brings up an important
Page 76 and 77: whether you want to have a palette
Page 78 and 79: Task analysis which includes identi
Page 80 and 81: MODULE 2 UNIT 3 USER CENTERED DESIG
Page 82 and 83: or small body text is also hard to
Page 84 and 85: Introduction to User-centered desig
Page 86 and 87: organizations themselves. Interacti
Page 88 and 89: After thorough analysis using vario
Page 90 and 91: Interaction design which is the dis
Page 92 and 93: In human-computer interaction and c
Page 94 and 95: The preferred method for ensuring u
Page 96 and 97: 3.4 ISO STANDARDS FOR USABILITY ISO
Page 98 and 99: In this unit, you have been introdu
Page 100 and 101: affect the way the command is execu
Page 102 and 103: • Guides the user via the predefi
Page 104 and 105: The term direct manipulation was in
Page 106 and 107: There are two important reasons for
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Page 110 and 111: UNIT 1 PROTOTYPING Table of Content
Page 112 and 113: Figure 12: The iterative steps of p
Page 114 and 115: select print Figure 13: An interfac
Page 116 and 117: Ambler, S.W. & Constantine, L.L. (2
Page 118 and 119: 3.2 LOW-FIDELITY PROTOTYPES Low-fid
Page 120 and 121: Figure 14:- Example of Sketching II
Page 122 and 123: Much more important for features th
Page 124 and 125: DENIM, an extension of SILK, is a t
Page 128 and 129: Another problem is that native widg
Page 130 and 131: interfaces, so that a realistic sim
Page 132 and 133: UNIT 3 INPUT AND OUTPUT MODELS Tabl
Page 134 and 135: Recall that perceptual fusion means
Page 136 and 137: 3.2 OUTPUT MODEL There are basicall
Page 138 and 139: directly-mapped pixel image will no
Page 140 and 141: Most stroke models also include som
Page 142 and 143: UNIT 4 MODEL VIEW-CONTROLLER (MVC)
Page 144 and 145: 3.3.2 AS A DESIGN PATTERN MVC enco
Page 146 and 147: The Views are XForms controls for s
Page 148 and 149: UNIT 5 LAYOUTS AND CONSTRAINTS Tabl
Page 150 and 151: 3.5 CONSTRAINTS Constraints are rel
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Page 154 and 155: MODULE 4 UNIT 1 TECHNIQUES FOR EVAL
Page 156 and 157: a. Card Sorting Card sorting is a w
Page 158 and 159: Rapid prototyping is a method used
Page 160 and 161: 3.2.1 THE USE OF PROTOTYPES It is o
Page 162 and 163: Dumas, J.S. and Redish, J.C. (1999)
Page 164 and 165: the users' respect for you as a pro
Page 166 and 167: the users will be and what kind of
Page 168 and 169: speed whenever the average load was
Page 170 and 171: Table 4:- Table: Average times for
Page 172 and 173: phases: list the actions, and then
Page 174 and 175: Nielsen and Molich used their own e
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7.0 REFERENCES AND FURTHER READING
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users. If you do not, you can be ba
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If you are led to develop more and
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It's very easy to shape the comment
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a. Analyzing the Bottom-Line Number
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you use. But then you need some way
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ecruit test users with more similar
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MODULE 4 UNIT 4 OTHER EVALUATION IS
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3.2 CURRENT ISSUES CONCERNING EVALU
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2.0 OBJECTIVES By the end this unit
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It provides a real focal point for
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3.3.4 CONDUCTING THE TEST Having co
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The stages involved in usability te
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