User Interface Styles
The user interface determines how information is entered in a DSS and how it is displayed by a DSS. The interface also determines the ease and simplicity of learning and using the system. There are four general structures or interface styles that can be used to control interactions with computerized information systems. These styles are 1) command-line interfaces, 2) menu interfaces, 3) point-and-click graphical interfaces, and 4) question-and-answer interfaces. Each style can be used in creating DSS user interfaces. The styles can often be combined usefully in a single application or set of related applications [see Galitz (1985); Shneiderman (1992); and Turban (1993)]. When building a user interface a designer should try to provide multiple ways to perform the same task. For example, a design may include a command-line interface, pull down menus for commands, and keyboard command equivalents. Many input devices including keyboard, mouse, touch pad, and voice inputs can be used to manipulate these four general interface styles.
Command-line interfaces are the oldest form of computer control. They originated when each command to a program was entered on a punched card. Commands still dominate user interaction with operating systems, including MS-DOS, UNIX, and Linux. In a DSS with a command language style interface, a user enters a command such as "run" or "plot". Many commands are composed of a verb-noun combination (for example "plot sales"). Command-line interfaces require a user to enter a command telling the system what to do next. It is the user's responsibility to know what commands are available and how to phrase those commands with their parameters. Such interfaces can be quite powerful, giving their users detailed control over system operation, but there is a penalty. Command interfaces are hard to learn. Most people never learn more than a fraction of the commands in any command language and make frequent mistakes in command entry. While command entry mistakes can usually be corrected, they create a cost for users and companies in terms of productive time lost and they can make users feel frustrated and incompetent.
In a menu interaction a user selects from a list of possible choices the task or function to be performed. The ordered list of functions or tasks is called a menu. The user makes a choice among items by manipulating an input device or entering a menu item number. Menus appear in a logical, hierarchical order, starting with a main menu and going to subordinate or sub-menus. Menus can become tedious and time consuming when complex situations are analyzed, since it may take several menus to build or use a system and the user must shift back and forth among the menus. A pull-down menu is a sub-menu that appears as a superimposed drop-down menu on a screen, usually after an entry has been made in a high level menu. Figure 5.2 shows a menu hierarchy in Microsoft Excel. The tools bars with graphical icons also serve as menus.
A graphical user interfaces (GUI) is an interface system in which users have direct control of visible objects. Users point and click to initiate actions rather than enter complex commands. The best known GUI is the Windows 95/98 operating system followed closely by the Macintosh OS. The major GUI elements are windows, icons, pull-down menus, and dialog boxes. A window is an area of the computer screen that behaves as if it was an independent computer terminal. Icons are small pictures that represent windows or actions. Some of the icons frequently used in Microsoft applications are shown in Figure 2. Clicking on an icon initiates opening a window or initiating a command. In the graphical or object manipulation interface style, the user directly manipulates objects represented as icons (or symbols).
Figure 5.3 Examples of Icons
User interfaces can be enriched with the use of multimedia and hypermedia technologies. Multimedia refers to many media including graphic materials, audio especially sound digitizing, and motion images including motion pictures and animation. Hypermedia describes documents that contain several types of media linked in documents. The World-Wide Web is an example of a hypermedia delivery system. Web documents can include explicit internal and external links, multimedia content, and interactivity with databases.
A question and answer interface dialogue begins with the computer asking the user a question. The user answers the question with a phrase or a sentence. A dialogue then occurs between the computer and user. The computer's questions are a function of prior responses of the user and the processing needs of the application. A related interface style is called form interaction; in form interaction style the user enters data or commands into designated spaces (fields) in a form. The headings of the form serve as a prompt for the desired input. A human-computer interaction that is similar to a human-human dialog is referred to as natural language dialogue. The major limitation of using natural language responses is the inability of the computer to really understand unstructured or unanticipated natural language. The programmer must anticipate user answers and program responses.
The following example shows a simple question and answer dialogue:
>dss What is your name?
>user Daniel Power
>dss What is your age?
>user 39 years old
>dss Please enter only a number
A question and answer dialogue is one of the oldest types of interfaces; it is not used as frequently today in building DSS, but it may be revived by improvements in speech recognition technologies. Another new type of interface is called a three-dimensional (3-D) or virtual reality (VR) interface. It is being used in a number of research settings. With a 3-D interface, user interacts with a 3-D computer-generated environment. A user wears a headset and hand position sensor to interact with the 3-D environment. The user can walk around, grasp and move objects, and in general alter the environment. A 3-D interface may become a viable DSS user interface in the future, but for the next few years managers and DSS analysts should focus on the interfaces discussed in preceding paragraphs. In most DSS more than one interface style will be implemented.
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