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Discourse Relations: A Structural and Presuppositional Account Using Lexicalised TAG

What it is about

The paper argues that many discourse relations do not have to be carried by discourse structure. Some are carried by anaphoric presuppositions (van der Sandt 1992) that are licensed by eventualities the hearer is taken to share. Discourse structure is kept bare: lexicalised tree-adjoining grammar (LTAG) trees, with connectives as anchors. Words such as "then", "for example", "otherwise" and "too" presuppose a shared item and link to it, and the link is not structural. The authors give examples where a link to a non-adjacent event crosses a structural link, as in the "On the one hand ... then ... because" sequence. They distinguish the sources of the presupposition by type: a shared eventuality for temporal adverbs such as "then", a generalisation for "for example", a complementary modal base for "otherwise", and an alternative for "instead" and "rather". The paper contains no numbers. Its proposed next step is a corpus annotation of anaphoric presuppositions, starting from the 350 cue phrases listed by Knott (1996).

Ideas

For Mova

The chapters are languages/en/36-discourse-relations.md and languages/en/33-implicature-and-presupposition.md, with languages/en/35-reference-and-coreference.md for the anaphoric side. The code is prag/src/infer.rs and world/src/qud.rs. The measure is the accuracy of the licensing rule on constructed and lesson examples, run twice, with the no-generalisation control.

Library summary

The Research library's own summary of the paper, in our words — not the paper's text.

Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "CC BY-NC-SA 3.0 (ACL Anthology, before 2016)" does not allow redistributing the text itself. Original — aclanthology.org/P99-1006.pdf

Summary

Most theories of discourse structure try to encode every semantic relation between clauses as a structural link. When a clause relates to several earlier ones, this produces graphs with crossing dependencies instead of trees, which makes a clean compositional semantics hard to define. Webber, Knott, Stone and Joshi propose dividing the work among three sources:

  • Structure. A minimal discourse structure is built from Lexicalised TAG (LTAG) elementary trees, anchored by connectives, punctuation or lexically empty feature structures. The trees combine through substitution and adjoining, which yields non-defeasible compositional meaning.
  • Inference. Defeasible reasoning from world knowledge and usage conventions then enriches that meaning.
  • Presupposition. Many adverbial connectives contribute relations through anaphoric presupposition (Van der Sandt, 1992). Like pronouns, these are resolved against shared knowledge, often the preceding discourse.

Because presuppositional links are not structural, they can cross structural boundaries while the discourse structure stays a tree. The account is theoretical and argued through constructed examples. It reuses clause-level semantic machinery and may generalise better across languages.

Key points

  • Diagnostic for structural vs. anaphoric arguments. Crossing structural links are forbidden, so an argument that can reach across one must be anaphoric. Subordinators ("because", "although") and paired frames ("On the one hand… On the other hand", "Not only… But also") are treated as structural. "Then" takes one argument structurally and the other by presupposition.
  • "For example". What it presupposes is a set of eventualities known to both speaker and hearer, and what it claims is that its own clause is one member of that set. The set can be licensed explicitly by "because". It can also come from causality inferred when two sentences are simply juxtaposed, and that inferred causality can be denied without contradiction.
  • "Otherwise". It presupposes a set of possible worlds taken from prior context and asserts what holds in the complementary worlds. It works with modal clauses and can co-occur with an explicit "because", as in "because otherwise". The authors keep presupposition separate from implicature.
  • Contrast with SDRT. Asher and Lascarides' (1999) version of SDRT attaches all material through rhetorical relations. The authors argue that items like "too" are more simply explained as presupposing a similar eventuality.
  • Future work. The authors call for:
    • precise semantics for connectives;
    • study of the attentional behaviour of presuppositions, which they compare to the information status of NPs;
    • a corpus annotation effort for anaphoric presuppositions;
    • evidence of practical benefit for NL understanding and generation.

Topics: Discourse analysis · Coreference resolution

Cite

The paper itself, not this card. BibTeX from the library's record of the work. DOI 10.3115/1034678.1034695

@inproceedings{webber1999discourse,
  title = {{Discourse Relations: A Structural and Presuppositional Account Using Lexicalised TAG}},
  author = {Webber, Bonnie and Knott, Alistair and Stone, Matthew and Joshi, Aravind},
  booktitle = {Proceedings of the 37th Annual Meeting of the Association for Computational Linguistics},
  year = {1999},
  doi = {10.3115/1034678.1034695},
  url = {https://doi.org/10.3115/1034678.1034695}
}

References

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