Conceptual and Linguistic Decisions in Generation

Conceptual and Linguistic Decisions in Generation Laurence DANLOS LADL (CNRS) Universit~ de Paris 7 2, Place Jussieu 7S00S Paris, France ABSTRACT Generation of texts in natural language requires making conceptual and linguistic decisions. This paper shows first that these decisions involve the use of a discourse grammar, secondly that they are all dependent on one another but that there is a priori no reason to give priority to one decision rather than another. As a consequence, a generation algorithm must not be modularized in components that make these decisions in a fixed order. 1. Introduction To express in natural language the information given in a semantic representation, at least two kinds of decisions have to be made: "conceptual decisions" and "linguistic decisions". Conceptual decisions are concerned with questions such as: in what order must the information appear in the text? which information must be expressed explicitly and what can be left implicit? Linguistic decisions deal with questions such as: which lexical items to choose? which syntactic constructions to choose? how to cut the text into paragraphs and sentences? The purpose of this paper is to show that conceptual decisions and linguistic decisions cannot be made independently of one another, and therefore, that a generation system must be based on procedures that promote intimate interaction between conceptual and linguistic decisions. In particular, our claim is that a generation process cannot be modularized into a "conceptualizer" module making conceptual decisions regardless of any linguistic considerations, passing its output to a "dictionary" module which would figure out the lexical items to use accordingly, which would then in turn forward its results to a "grammar", where the appropriate syntactic constructions are chosen and then developed into sentences by a "syntactic component". In such generation systems (cf. (McDonald 1983) and (McKeown 1982)), it is assumed that the conceptualizer is language-free, i.e., need have no linguistic knowledge. This assumption is questionable, as we are going to show. Furthermore, in such modularized systems, the linguistic decisions must, clearly, be made so as to respect the conceptual ones. This consequence would be acceptable if the best lexical choices, i.e., the most precise, concise, evocative terms that can be chosen, always agree with the conceptual decisions. However, there exist cases in which the best lexical choices and the conceptual decisions are in conflict. To prove our theoritical points, we will take as an example the generation of situations involving a result causation, i.e., a new STATE which arises because of one (or several) prior ACTs (Schank 1975). An illustration of a result causation is given in the following semantic representation (A) CRIME : ACT =: SHOOTING ACTOR --> HUMO =: 3ohn SHOOTING:AT --> HUMI =: Mary BODY-PART =: HEAD ===> STATE =: DEAD OB3ECT --> HUMI which is intended to describe a crime committed by a person named John against a person named Mary, consisting of John's shooting Mary in the head, causing Mary's death. 2. Conceptual decisions and lexical choice Given a result causation, one decision that a …

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