The Computational Complexity of Avoiding Conversational Implicatures
Summary
The paper asks how a natural language generation system can choose referring expressions that do not lead listeners to draw unintended conversational implicatures (Grice 1975). For example, describing the only table in a room as "brown" and "wooden" suggests those details matter. Building on Dale's (1989) distinguishing-description model, Reiter treats a referring expression as a classification plus attribute-value pairs. He recasts Grice's maxims, along with the basic-level effects observed by Cruse and Hirschberg, as a trio of preference rules: a Lexical Preference rule, a rule of Local Brevity, and a constraint requiring No Unnecessary Components. A description counts as free of false implicatures when no other successful description is preferred over it. Reiter shows that descriptions that are maximal under these rules can be generated in polynomial time. Stricter alternatives, such as Full Brevity (always the shortest description) and No Unnecessary Words, make generation NP-Hard. The work matters because it uses computational cost alongside linguistic plausibility to decide how pragmatic constraints should be formalized in NLG.
Key points
- The model treats successful descriptions and the preference relation as a partially ordered set, similar to Hirschberg's (1985) account of scalar implicatures. Choosing any description implies that no higher-ranked alternative was available.
- Full Brevity is NP-Hard under every length measure the author examined: open-class words, words, characters, and components.
- An exhaustive shortest-first search needs 6 steps for the toy example (N=3, L=2). It needs 175 checks for L=3, N=10, more than 6000 for L=4, N=20, and more than 2,000,000 for L=5, N=50.
- Lexical Preference generalizes the preference for basic-level classes (Rosch 1978). Using a lexical class implies that no preferred class could have been used instead.
- The rules can conflict when a basic-level class needs several words, as with Washing-Machine versus Appliance or Machine. In such cases the basic-level preference should take priority.
Cited by
- Computational Interpretations of the Gricean Maxims in the Generation of Referring Expressions
- Conversational Implicatures in Indirect Replies
- The Gricean Maxims in NLP — A Survey
Cite
@inproceedings{reiter1990computational,
title = {{The Computational Complexity of Avoiding Conversational Implicatures}},
author = {Reiter, Ehud},
booktitle = {28th Annual Meeting of the Association for Computational Linguistics},
year = {1990},
doi = {10.3115/981823.981836},
url = {https://doi.org/10.3115/981823.981836}
}References
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