--- title: "Discourse Relations and Defeasible — Lascarides 1991" description: "The paper addresses why short texts with nearly identical syntax get different temporal readings." authors: ["Alex Lascarides", "Nicholas Asher"] year: 1991 venue: "29th Annual Meeting of the Association for Computational Linguistics" source: "https://aclanthology.org/P91-1008/" doi: "10.3115/981344.981352" licence: "CC BY-NC-SA 3.0 (ACL Anthology, before 2016)" licence_url: "https://creativecommons.org/licenses/by-nc-sa/3.0/" summary_licence: "Elamur Cosmic License" canonical: "https://research.elamur.ai/free/papers/lascarides-1991-discourse-relations-defeasible-knowledge/" --- [Elamur Research](https://md.research.elamur.ai/) · [this page in HTML](https://research.elamur.ai/free/papers/lascarides-1991-discourse-relations-defeasible-knowledge/) [home](https://md.research.elamur.ai/) / [papers](https://md.research.elamur.ai/free/papers/) / [1991](https://md.research.elamur.ai/free/papers/1991/) / Discourse Relations and Defeasible Knowledge # Discourse Relations and Defeasible Knowledge **Authors:** [Alex Lascarides](https://md.research.elamur.ai/free/authors/alex-lascarides/), [Nicholas Asher](https://md.research.elamur.ai/free/authors/nicholas-asher/) · **Year:** 1991 · **Venue:** 29th Annual Meeting of the Association for Computational Linguistics · **Licence:** [CC BY-NC-SA 3.0 (ACL Anthology, before 2016)](https://creativecommons.org/licenses/by-nc-sa/3.0/) **Links:** [Publisher's page](https://aclanthology.org/P91-1008/) · [PDF](https://aclanthology.org/P91-1008.pdf) · [DOI 10.3115/981344.981352](https://doi.org/10.3115/981344.981352) · [OpenAlex](https://openalex.org/W2163214273) **Citations:** 151 citations (openalex-snapshot · 2026-10-14) · [26](#cited-by) in our library, of the 140673 papers whose bibliographies we read ## Summary The paper addresses why short texts with nearly identical syntax get different temporal readings. In "Max stood up. John greeted him" the events follow the order in which they are told. In "Max fell. John pushed him" the second event comes first and causes the first. Since the logical forms are alike, the authors argue that sentence form alone cannot settle the order, and earlier accounts (e.g. Webber 1988, Dahlgren 1988) cannot explain all such cases or lack a proper inference mechanism. They propose a formal theory in which discourse relations are inferred by default reasoning in MASH, a modal logic for nonmonotonic inference by Asher & Morreau. Two kinds of default rules are encoded: - causal world knowledge, such as pushing normally causing falling; - Gricean-style pragmatic maxims, such as telling events in the order they happened. Different readings then follow from standard patterns of default inference, chiefly Penguin-style specificity and the Nixon Diamond. This gives a principled, inference-driven model of how temporal and discourse structure are built from text. The paper is purely theoretical: it uses no corpus or evaluation data. ## Key points - **Discourse relations covered:** Narration, Elaboration, Explanation, Background and Result. More than one relation may hold between the same two clauses. - **Default order rule:** Narration applies by default, and an indefeasible axiom says the events then occur in textual order. Specific causal laws, combined with the axiom that causes precede effects, override this through a "Complex" Penguin Principle, which yields Explanation for the falling/pushing example. - **Background vs. Result:** chains of default conflicts (a "Cascaded" Penguin Principle, plus a default that states overlap) yield Background for "The room was pitch dark" after opening a door. The same sentence yields Result after switching off the light. The two relations are shown to be mutually inconsistent. - **Discourse popping:** an unresolvable Nixon Diamond/Polygon conflict blocks attaching a new clause to an embedded one. The clause must then attach higher up, as in the Guy/dancing-competition example. - **Scope and follow-up:** the analysis is limited to texts in the simple past that contain no additional time-related expressions. The approach is reported as extending to the pluperfect (Lascarides & Asher 1991), and temporal connectives and adverbials are left for future work. *Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.* Fields: [Linguistics & languages](https://md.research.elamur.ai/free/shelves/linguistics/) Topics: [Discourse analysis](https://md.research.elamur.ai/free/topics/discourse-analysis/) ## Cited by Cited by 26 papers of our library cite it (of the 140673 whose bibliographies we read); 5 of them have a page here, 21 not yet. - [A Hybrid Reasoning Model for Indirect Answers](https://md.research.elamur.ai/free/papers/green-1994-hybrid-reasoning-model-indirect-answers/) - [Interpreting and Generating Indirect Answers](https://md.research.elamur.ai/free/papers/green-1999-interpreting-generating-indirect-answers/) - [COMET-ATOMIC 2020: On Symbolic and Neural Commonsense Knowledge Graphs](https://md.research.elamur.ai/free/papers/hwang-2020-comet-atomic-2020-symbolic-neural/) - [Neural Net Models of Open-domain Discourse Coherence](https://md.research.elamur.ai/free/papers/li-2017-neural-net-models-open-domain/) - [Representing Discourse Coherence: A Corpus-Based Study](https://md.research.elamur.ai/free/papers/wolf-2005-representing-discourse-coherence-corpus-based/) ## Cite The paper itself, not this page. BibTeX from the library's record of the work. ```bibtex @inproceedings{lascarides1991discourse, title = {{Discourse Relations and Defeasible Knowledge}}, author = {Lascarides, Alex and Asher, Nicholas}, booktitle = {29th Annual Meeting of the Association for Computational Linguistics}, year = {1991}, doi = {10.3115/981344.981352}, url = {https://doi.org/10.3115/981344.981352} } ``` - [← previous Capturing Language-Specific Semantic Distinctions in Interlingua-based MT](https://md.research.elamur.ai/free/papers/barnett-1991-capturing-language-specific-semantic-distinctions/) - [next → EUROTRA: an assessment of the current state of the EC's MT programme](https://md.research.elamur.ai/free/papers/arnold-1991-eurotra-assessment-current-state-ec/) - [↑ back to papers of 1991](https://md.research.elamur.ai/free/papers/1991/) ## References 22 references, 0 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet. 1. 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