Mayhew's Book (chapt. 7)

Designing Command Languages

Command Language Semantics

• Balance power and simplicity (richness and minimality, respectively) according to user needs.

Command Language Syntax

• Provide consistency in syntax.

• Use an action-object syntax.

• Avoid arbitrary use of punctuation.

• Avoid positional grammars.

• A command language syntax should be natural and mnemonic.

• Allow defaulting of optional parameters.

• Avoid frequent use of shift or control keys.

Command Language Lexicon

• Design command names to be hierarchical, congruent, specific, familiar, consistent in grammatical form, and discriminable.

• Use user jargon and avoid computer jargon.

• Use a simple, consistent rule for command name abbreviations.

• Allow full command names and emphasize them in training, even if abbreviations are allowed.

Command Language Interaction

• Locate the command line at the bottom of the screen or window, unless it is clear that the user's eyes will be elsewhere at input time.

• Provide interactive support through defaults, command editing, intelligent interpretation, type-ahead, and feedback.

• Provide memory aids such as on-line quick reference and prompting.

• Provide function keys for high-frequency commands.