exercises

3. the interaction

EXERCISE 3.7

Describe briefly four different interaction styles used to accommodate the dialog between user and computer.

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These are the commonest interaction styles:

Command line interface Provides a means of expressing instructions to the computer directly, using function keys, single characters, abbreviations or whole-word commands. In some systems it is the only way of communicating with the system, e.g. remote access using telnet. More commonly it supplements menu-based interfaces, giving experienced users accelerated access to the system's functionality. Flexible and powerful but may be difficult to learn and use. Because commands must be remembered it is better for expert users than novices.

Menus The set of available options is displayed on the screen, and selected using the mouse, or numeric or alphabetic keys. These visible options rely on recognition rather than recall, but still need to be meaningful and logically grouped. Menus may be nested hierarchically, with the grouping and naming of menu options the only cue for finding the required option. May be text based or have a graphical component.

Natural language Understanding of speech and written input is the focus of much research. Natural language is very difficult for a machine to understand. It is ambiguous, syntactically and semantically. It is difficult to provide the machine with context. Unlikely that a general natural language interface will be available soon, but systems can be built to understand restricted subsets of a language. They are limited and the user has to learn what the computer understands.

Question/answer, query dialogue Question/answer dialogue is a simple mechanism for providing input to an application in a specific domain. The user is asked a series of questions (mainly with yes/no responses, multiple choice, or codes) and is led through the interaction step by step. Easy to learn and use, but limited in functionality and power. Appropriate for restricted domains and novice/casual users. Query languages are used to construct queries to retrieve information from a database. They use natural-language-style phrases, but require specific syntax and knowledge of the database structure. Their effective use requires some experience.

Form-fills and spreadsheets Used primarily for data entry but also useful in data retrieval. The display resembles a paper form, with slots to fill in. May be based on an actual form with which the user is familiar. Easy to learn and use for novice users and can be flexible for expert users. Spreadsheets are a variation. Users can enter and alter values and formulae in any order. The system will maintain consistency amongst the values displayed, ensuring that all formulae are obeyed, so users can manipulate values to see the effects of changing different parameters. Flexible and natural, as the distinction between input and output is blurred.

WIMP interface Also often called simply windowing systems. WIMP stands for windows, icons, menus and pointers (sometimes windows, icons, mice and pull-down menus), and is the default interface style for the majority of interactive computer systems in use today, especially in the PC and desktop workstation arena. Examples of WIMP interfaces include Microsoft Windows for IBM PC compatibles, MacOS for Apple Macintosh compatibles and various X Windows-based systems for UNIX.

Mixed styles In UNIX windowing environments the contents of many windows are often simply command line or character-based programs. Mixing of interface styles in the same system is quite common, especially where older legacy systems are used at the same time as more modern applications. Can be a problem if users try to use commands and methods suitable for one environment in another, leading to inconsistency in the interface.

Point-and-click interfaces In most multimedia systems and web browsers, most actions take only a single click of the mouse button. The philosophy is simpler than WIMP and more closely tied to ideas of hypertext. Not tied to mouse-based interfaces, but also used in touchscreen information systems, often combined with a menu-driven interface. Has been popularized by World Wide Web pages, which incorporate different types of point-and-click navigation: highlighted words, maps, iconic buttons.

Three-dimensional interfaces Increasingly used in interfaces. Virtual reality is an obvious example, but ordinary WIMP elements, buttons, scroll bars, etc., can be given a 3D appearance using shading. Can highlight active areas if used discriminatingly. Other techniques: 3D workspaces, VR and information visualization systems, where the user can move about within a simulated 3D world. 3D interfaces invite use of real world abilities in the electronic world.

Other exercises in this chapter

ex.3.1 (ans), ex.3.2 (ans), ex.3.3 (ans), ex.3.4 (open), ex.3.5 (open), ex.3.6 (tut), ex.3.7 (tut), ex.3.8 (open), ex.3.9 (tut), ex.3.10 (open), ex.3.11 (tut), ex.3.12 (tut)

all exercises for this chapter