Copyright © 2005, Pearson Education, Inc. Chapter 8 Command and Natural Languages

Copyright © 2005, Pearson Education, Inc. The Basic Goals of Language Design Precision Compactness Ease in writing and reading Speed in learning Simplicity to reduce errors Ease of retention over time

Copyright © 2005, Pearson Education, Inc. Higher-Level Goals of Language Design Close correspondence between reality and the notation Convenience in carrying out manipulations relevant to user's tasks Compatibility with existing notations Flexibility to accommodate novice and expert users Expressiveness to encourage creativity Visual appeal

Copyright © 2005, Pearson Education, Inc. Functionality to Support User’s Tasks Designers should determine functionality of the system create a list of task actions and objects develop a set of interface actions and objects create a table of user communities and tasks, with expected use frequency determine hierarchy of importance of user communities (i.e. prime users) evaluate destructive actions (e.g. deleting objects) to ensure reversibility identify error conditions and prepare error messages allow shortcuts for expert users, such as macros and customizing system parameters

Copyright © 2005, Pearson Education, Inc. 1.Simple truncation: The first, second, third, etc. letters of each command. 2.Vowel drop with simple truncation: Eliminate vowels and use some of what remains. 3.First and last letter: Since the first and last letters are highly visible, use them. 4.First letter of each word in a phrase: Use with a hierarchical design plan. 5.Standard abbreviations from other contexts: Use familiar abbreviations. 6.Phonics: Focus attention on the sound. Six Potential Abbreviation Strategies

Copyright © 2005, Pearson Education, Inc. Command-language guidelines 1.Create explicit model of objects and actions 2.Choose meaningful, specific, distinctive names 3.Try to achieve hierarchical structure 4.Provide consistent structure (hierarchy, argument order, action-object) 5.Support consistent abbreviation rules (prefer truncation to one letter) 6.Offer frequent users the ability to create macros 7.Consider command menus on high-speed displays 8.Limit the number of commands and ways of accomplishing a task

Copyright © 2005, Pearson Education, Inc. Natural Language in Computing Natural-language interaction Natural-language queries and question answering –INTELLECT system: 400 installations in the ’80s –1999 Sql Server: English Query Text-database searching –Uses filters for commands Natural-language text generation –Simple tasks: weather reports Adventure games and instructional systems –Provides feedback and guidance

Copyright © 2005, Pearson Education, Inc. Summary 1.Command languages attractive Frequent use of system is anticipated Users are knowledgeable about the task and the interface Screen space is at a premium Response time and display rates are slow Numerous functions can be combined 2.Designers should design for functionality 3.Natural languages have limited effectiveness and advantages – too much ambiguity