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inferences.isnowknowntermsof this criterionto distinguishbetweenprojects whichsatisfyit andthosewhichdonot.

6.3 Natural Language and Other Man-Machine Communication It is common sense that various specific communication goals are best served by different forms of exchange. This notion is borne out by the tendency in technical fields of human activity to spawn jargon which only slowly (if ever) filters into more widespread usage. In the general area of communication between man and machine, a few tasks are already well handled by available languages. For example, in the area of numerical computations the present formal languages, while not perfect, are highly serviceable. When one considers the introduction of sophisticated computer systems into environments where it is necessary for them to communicate frequently, competently, and rapidly with people who are not specialists in computer programming, then the need for improvement in man machine communication capability quickly becomes apparent. A natural language capability in computers is required primarily in two kinds of circumstances -(1) where the nature of the information to be transferred warrants the flexibility and generality of a natural language, in distinction to a more specialized language, and (2) where, because of the number, nature, or condition of the humans involved, it is impractical to have the humans communicate in a formal language. There are additional considerations of convenience to the user, and attracting users who otherwise might be reluctant to use the available computer facilities. For directing the global actions of robot devices of all kinds, as well as the interrogation of question-answering systems, the ability to use natural language considerably eases or eliminates the problem of training individuals to use these resources. In particular, the user population of an Earth-sensing information system can be significantly and economically extended through direct communication between users and the system in natural language. Unfortunately, at present the domain is essentially that of a research domain, with relatively few natural language interfaces operating in production environments. Man-machine information exchanges can be segregated into iconic communication, such as pictures, and symbolic communication, such as formal computer languages and human natural language (see fig. 6.2). These differ significantly in the amount and kind of interpretation required to understand and to react to them. For instance, formal computer languages are largely designed to be understood by machines rather than people. For purposes of further discussion, man-machine communication is subcategorized as follows: (1) Machine understanding of keyed (typed) natural language (2) Machine participation in natural language dialogue (3) Machine recognition/understanding of spoken language (4) Machine generation of speech (5) Visual and other communication (includes iconic forms).

6.3.1 Keyed Natural Language and Man-Machine Dialogue In those instances in which the environment is highly restricted with respect to both the domain of discourse (semantics) and the form of statements which are appropriate (syntax), serviceable interfaces are just becoming possible with state-of-the-art techniques. Primary examples are the LUNAR (Woods et al., 1972) and SOPHIE (Brown and Burton, 1975) systems. However, any significant relaxation of semantic and syntactic constraints produces very difficult problems in AI. Intensive research is presently underway in this area. It seems that the semantic aspects of normal human use of language override a large part of the syntactical aspects. Computer languages traditionally have been almost entirely syntax-oriented, and so the considerable knowledge available concerning them has very little relevance in the natural language domain. Progress in flexible natural language interfaces is likely to be tied to progress in areas such as representation of knowledge and "common sense" reasoning. These lie at the heart of intelligent information processing -full natural language competency at the level of human performance requires a machine with intelligence and world knowledge comparable to that of humans. At this time there is little work in progress on the necessity or appropriateness of specialized hardware for natural language processing. Accepting the close relationship between human-grade natural language proficiency and general intelligence level, and the improbability of near-term attainment of humangrade general intelligence in machines, it is appropriate to focus instead on achieving usable natural language interfaces at a lower level of machine performance. This leads to an examination of man-machine dialogues in which the goal of the man is to communicate a clear and immediate statement of information, or a request for information or action, to the machine, where the information or request is in a domain for which the machine has a competent model. In this sphere of activity the following component capabilities are thought to be highly desirable, and probably necessary, for efficient and effective communication: domain model, user model (general, idiosyncratic, contextual), dialogue model, explanatory capability, and reasonable default assumptions.