Parsing into Discourse Object Descriptions

e Parsing into Discourse Object Descriptions Lars Ahrenberg Department of Computer and Information Science Link6ping University S - 581 83 Link~ping ABSTRACT This paper reports work on the design of a natural language interface with a limited dialogue capability. It is argued that (i) The interpretation of the input is preferably represented as a structure of Discourse Object Descriptions (DODs); (ii) The DODs must be determined on the basis of different types of knowledge such as grammatical knowledge, object type deirmitions and knowledge about existing discourse objects and their discourse status; (iii) The different types of knowledge are stored separately but integrated in the interpretation process which is based on constraints. INTRODUCTION The LINLIN-project is concerned with the development of general-purpose natural language interfaces (NLIs) to computer software with special emphasis on communication in Swedish. A useful general-purpose NLI must meet a var/ety of requirements, a number of which concern communicative ability. The communicative abilities of as NLI are necessarily restricted by the limitations of existing techniques, but can also be purposely restricted to enhance transparency. It is not certain that the linguistically more competent NLI is the most useful one, e.g. if its behaviour appears idiosyncratic to the user. In any case, the language of an NLI is a language designed (and is in that respect not a natural language) so there are many questions to be answered about how it should be designed, both in terms of how it should function as a vehicle of communication and in terms of internal representations and procedures. As for the first aspect we are conducting a series of simulations to fred out what communicative abilities an NLI should have (Dahlb~k&J~neson, 1986), but meanwhile we are assuming that LINLIN should meet the following demands: it should have a fair knowledge of the structure of Swedish words, clauses and utterances, an s This work is part of the project Analysis and Generation of Natural-Lan~,ruage Texts supported by the National Swedish Board of Technical Development. extendable lexicon, an extendable knowledge of object types, an ability to cope with directives, questions and assertions as they relate to the current background system(s) and a restricted ability to engage in a dialogue with the user. The dialogue capabilities of LINLIN are primarily designed for the following purposes: (a) to enable the user to make explicit and implicit cross-references between utterances, e.g. by using pronouns and ellipsis; (b) to allow the user to build commands incrementally; (c) to ask the user for clarifications and other information that the system might need, and (d) to provide help for the user. In this paper some consequences of these demands for the representation and interaction of various types of knowledge that the system needs are considered. The main ideas are t~e following: (1) The content of user inputs is preferably represented as a structure of Discourse Object Descriptions (DODs) which relate in various ways to objects of the universe of discourse. (2) Different types of knowledge, including object type knowledge and …

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