Dialog Metaphor is an interaction between the user and the system through Direct Manipulation Metaphor is an interaction between user and the

J.E.D.I

4.5.3 Screen and Dialog Design

The boundary classes are refined to define screens that the users will be using and the interaction dialog of the screens with other components of the software. In general, there are two metaphors used in designing user- interface are used.

1. Dialog Metaphor is an interaction between the user and the system through

the use of menus, function keys or entering of a command through a command line. Such metaphor is widely used in the structured approach of developing user-interfaces that are shown on character or text based terminals.

2. Direct Manipulation Metaphor is an interaction between user and the

system using graphical user interfaces GUIs. Such interfaces are event- driven, i.e., when a user, let say clicks a button event, the system will respond. It gives the user an impression that they are manipulating objects on the screen. For object-oriented development which uses visual programming integrated environments, we use the direct manipulation metaphor. However, when designing interfaces, several guidelines should be followed. Dialog and Screen Design Guidelines 1. Stick to the rule: ONE IDEA PER SCREEN. If the main idea changes, another screen must appear. 2. Standardize the screen layout. This would involved defining style guides that should be applied to every type of screen element. Style guides support consistency of interface. Consistency helps users learn the application faster since functionality and appearance are the same across different parts of the application. This applies to commands, the format of the data as it is presented to the user such as date formats, layout of the screens etc. Several software vendors provide style guides that you may use. Common style guides are listed below: ● Java Look and Feel Design Guidelines http:java.sun.com ● The Windows Interface Guidelines for Software Design http:msdn.microsoft.com ● Macintosh Human Interface Guidelines http:developer.apple.com 3. When presenting data items to users, always remember that: ● They should have a screen label or caption, and they should be the same throughout the entire application. As an example, you have a data item that represents a student identification number. You may decide to use Student ID as its caption. For every screen that display this item, use the value Student ID as the label; do not change it to Student Number or Student No.. ● As much as possible, they should be located on the same place in all screens, particularly, for the data entry screens. ● They should be displayed in the same way such as in the case of presenting dates. If the format of the dates follows MM-DD-YYYY format, then all dates should be displayed in this format. Do not change it. Software Engineering 173 J.E.D.I 4. For controllers that require a longer time to process, keep user informed of what is going on. Use XX completed messages or line indicators. 5. If possible, it would be wise to always inform the user of the next step. Wizard-type dialog design is always a good approach. 6. Provide meaningful error messages and help screens. AVOID PROFANITY Developing the Screen and Dialog Design STEP 1: Prototyping the User-interface. A prototype is a model that looks, and to some extent, behaves like the finished product but lacking in certain features. It is like an architects scale model of a new building. There are several types of prototypes.

1. Horizontal prototypes provide a model of the user interface. It deals only