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

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UNIT 4 MODEL VIEW-CONTROLLER (MVC) Table of Contents 1.0 Introduction 2.0 Objectives 3.0 Main Content 3.1 Model-View Controller 3.2 History 3.3 Pattern Description 3.4 MVC Implementation Framework 3.5 Implementations of MVC as GUI frameworks 4.0 Conclusion 5.0 Summary 6.0 Tutor Marked Assignment 7.0 Further Reading and Other Resources 1.0 INTRODUCTION The concept of Model View-Controller (MVC) is introduced in this unit. We will also discuss the history of MVC, pattern description, MVC implementation framework. Implementing MVC as GUI frameworks is also explained. 2.0 OBJECTIVES By the end this unit, you should be able to: Explain the term model view-controller (MVC) Have good knowledge of the history of MVC Explain pattern description and MVC implementation framework Describe how to implement MVC as GUI frameworks 3.0 MAIN CONTENT 3.1 MODEL VIEW-CONTROLLER Model–view–controller (MVC) is an architectural pattern used in software engineering. The pattern isolates business logic from input and presentation, permitting independent development, testing and maintenance of each. An MVC application is a collection of model/view/controller triplets (a central dispatcher is often used to delegate controller actions to a view-specific controller). Each model is associated with one or more views (projections) suitable for presentation (not necessarily visual presentation). When a model changes its state, it notifies its associated views so they can refresh. The controller is responsible for initiating change requests and providing any necessary data inputs to the model. 142
MVC is frequently and needlessly convoluted by tying it directly to a graphical user interface. That a controller is often driven indirectly from a GUI is incidental. Likewise, rendering views graphically is an application of MVC, not part of the pattern definition. A business-to-business interface can leverage an MVC architecture equally well. 3.2 HISTORY MVC was first described in 1979 by Trygve Reenskaug, then working on Smalltalk at Xerox PARC. The original implementation is described in depth in the influential paper "Applications Programming in Smalltalk-80: How to use Model–View–Controller". There have been several derivatives of MVC. For example, Model View Presenter is used with the .NET Framework, and the XForms standard uses a "model-view-controllerconnector architecture". However, standard MVC remains popular. 3.3 PATTERN DESCRIPTION Model–view–controller is both an architectural pattern and a design pattern, depending on where it is used. 3.3.1 AS AN ARCHITECTURAL PATTERN It is common to split an application into separate layers that can be analyzed, and sometimes implemented, separately. MVC is often seen in web applications, where the view is the actual HTML or XHTML page, and the controller is the code that gathers dynamic data and generates the content within the HTML or XHTML. Finally, the model is represented by the actual content, which is often stored in a database or in XML nodes, and the business rules that transform that content based on user actions. Though MVC comes in different flavors, control flow is generally as follows: The user interacts with the user interface in some way (for example, presses a mouse button). The controller handles the input event from the user interface, often via a registered handler or callback. The controller notifies the model of the user action, possibly resulting in a change in the model's state. (For example, the controller updates the user's shopping cart.) A view uses the model indirectly to generate an appropriate user interface (for example, the view lists the shopping cart's contents). The view gets its own data from the model. The model and controller have no direct knowledge of the view. The user interface waits for further user interactions, which restarts the cycle. Some implementations such as the W3C XForms also use the concept of a dependency graph to automate the updating of views when data in the model changes. By decoupling models and views, MVC helps to reduce the complexity in architectural design and to increase flexibility and reuse of code. 143
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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
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whether you want to have a palette
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Task analysis which includes identi
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MODULE 2 UNIT 3 USER CENTERED DESIG
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or small body text is also hard to
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Introduction to User-centered desig
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organizations themselves. Interacti
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After thorough analysis using vario
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Interaction design which is the dis
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Page 94 and 95: The preferred method for ensuring u
Page 96 and 97: 3.4 ISO STANDARDS FOR USABILITY ISO
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Page 110 and 111: UNIT 1 PROTOTYPING Table of Content
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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
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Page 124 and 125: DENIM, an extension of SILK, is a t
Page 126 and 127: • Encourage menu & forms style, r
Page 128 and 129: Another problem is that native widg
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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
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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
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Page 162 and 163: Dumas, J.S. and Redish, J.C. (1999)
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Page 176 and 177: 7.0 REFERENCES AND FURTHER READING
Page 178 and 179: users. If you do not, you can be ba
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Page 184 and 185: a. Analyzing the Bottom-Line Number
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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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