Grammatical and Ungrammatical Structures in User-Adviser Dialogues= Evidence for Sufficiency of Restricted Languages in Natural Language Interfaces to Advisory Systems

User-adviser dialogues were collected in a typed Wizardof-Oz study (=man-behind-the-curtain study*). Thirty-two users had to solve simple statistics problems using an unfamiliar statistical package. Users received help on how to use the statistical package by typing utterances to what they believed was a computerized adviser. The observed limited set of users' grammatical and ungrammatical forms demonstrates the sufficiency of a very restricted grammar of English for a natural language interface to an advisory sys* tem. The users' language shares many features of spoken face-to-face language or of language generated under realtime production constraints (i.e., very simple forms of utterances). Yet, users also appeared to believe that the natural language interface could not handle fragmentary or informal language and users planned or edited their language to be more like formal written language (i.e., very infrequent fragments and phatics). Finally, users also appeared to believe in poor shared context between users and computerized advisers and referred to objects and events using complex nominals instead of faster-to-type pronouns. I N T R O D U C T I O N It has been azgued that natural language interfaces with very rich functionality are crucial to the effective use of advisory systems and that interfaces using formal languages, menus, or direct manipulation will not suffice (Finin, Joshi, and Webber, 1986). Designing, developing, and debugging a rich natural language interface (its parser, grammar, recovery strategies from unparsable input, etc.) are timeconsuming and labor-intensive. Nevertheless, natural language interfaces can be quite brittle in the face of uncon* strained input from the user, as can be found in applications such as user-advising. One step toward a solution to these problems would be the identification of a subset of gram* matical and ungrammatical structures that correspond to the language generated by users in any user-advising situations, irrespective of the domain. This subset could be used to design a core grammar, strategies to handle ungrammatical input, and some parsing heuristics portable to any natural language interface to advisory systems. This strategy would increase the habitability of the natural language interface (Watt, 1968; Trawick, 1983) and reduce its development