Verbal (symbol) Based Interactions Dr.s Barnes and Leventhal

Reference  Chapter 8

Definition  Verbal (symbol) Based Interactions These include command-line, natural language and speech-based interactions

Command Line Interactions/General  Command languages rely on user recall of commands.  Examples: telnet interfaces to UNIX, dos

Command Line Interactions - Some Benefits  If the sequence of commands have a highly controlled structure, that structure may help novices form a conceptual model of the system.  Expert users may feel in control of systems with command line interfaces and be able to work at speeds that are appropriate for their skill level and sophisticated mental models.

Situations Which Call for Command Line Interactions  High levels of User Knowledge. Expert users have a highly developed mental model of the task that they want to do. A command line interaction should facilitate their ability to execute the steps for the task to match their mental models.  Low levels of User Knowledge PLUS tightly structured (not open) task. A constrained command line interface that mimics the tight structure of the task will help the novice to develop a mental model that matches the task. The command line interaction typically has less visual elements to distract the novice so the novice’s mental model should incorporate only the command steps that are relevant to the task.

Command Line Interactions - Design Guidelines  overheads

Command Line Interactions to Evaluate (use guidelines)  telegraf  vi editor

Natural language Interactions  The idea is that people could interact using their own natural language, such as English, French, Arabic and so on.  In this style of interaction, the burden of learning the “command” set is eliminated (users would still need to know WHEN to issue a particular instruction).  This is a really tough thing to do as natural language use is full of ambiguity. Also natural language is not static but is constantly evolving under the influence of culture, mixing of cultures and so on.  This is an area that has not fared well as a practical solution to user interface problems, partly because of the difficulty of implementing efficient systems.  Implementation is often based on AI techniques such as augmented transition networks.

Requirements for Natural Language Interaction  From Hayes and Reddy (1983)  Able to parse fragmented and ungrammatical input  Correctly interpreting utterances  Being able to explain what has and has not happened, been done and what cannot be done and what it is trying to do.  Being able to track the focus of a dialog  Identifying objects from descriptions  Generating descriptions that are appropriate for the context

Natural Language and Speech  Speech based interactions are a subset of natural language interactions.  Speech recognition refers to the ability of a computer system to recognize human speech.  Speech generation refers to the ability of a computer system to generate spoken strings.

What about the Practicality?  Speech and natural language interactions  Have the potential to facilitate interactions for people who would not be able to use alternative interaction styles  From the designers perspective, the problem can be “simplified” if the language and the grammar are constrained BUT the user then needs to learn the restricted language as well.