---
title: "Computation of a Subclass of Inferences: Presupposition and"
description: "Joshi and Weischedel study a narrow, well-behaved slice of natural-language inference: entailment… 23 references, cited by 3 papers here."
authors: ["Aravind K. Joshi", "Ralph Weischedel"]
year: 1977
venue: "eScholarship (California Digital Library)"
source: "https://aclanthology.org/J77-1008/"
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/en/papers/joshi-1977-computation-subclass-inferences-presupposition-entailment/"
---
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# Computation of a Subclass of Inferences: Presupposition and Entailment

**Authors:** [Aravind K. Joshi](https://md.research.elamur.ai/free/en/authors/aravind-joshi/) and [Ralph Weischedel](https://md.research.elamur.ai/free/en/authors/ralph-weischedel/) · **Year:** 1977 · **Venue:** [eScholarship (California Digital Library)](https://md.research.elamur.ai/free/en/venues/cl/) ([Computational Linguistics 1977](https://md.research.elamur.ai/free/en/venues/cl/1977/)) · **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/J77-1008/) · [PDF](https://aclanthology.org/J77-1008.pdf) · [OpenAlex](https://openalex.org/W6989933060)

**Citations:** 2 citations (OpenAlex, 2026-10-14) · [3](https://md.research.elamur.ai/free/en/papers/joshi-1977-computation-subclass-inferences-presupposition-entailment/cited-by/) in our library, of the 149,439 papers whose bibliographies we read

## Summary
Joshi and Weischedel study a narrow, well-behaved slice of natural-language inference: entailment and presupposition. Unlike open-ended conjecture, these hold in every context. S entails S′ when S′ is true wherever S is. S presupposes S′ when both S and its internal negation entail S′. The authors argue that such inferences are tied to word definitions and syntactic structure, so they can be computed structurally rather than by general deduction, which tends to blow up combinatorially. Their key notion is the "subformula-derived" inference: pick a well-formed piece of the sentence's meaning representation and apply a finite-state tree transformation to it. The only requirement is that the representation language has an approximately context-free syntax, so the method does not depend on any particular set of semantic primitives. They built an ATN-based system that computes these inferences during parsing. Lexical entries carry the transformations, and certain constructions, such as clefts, trigger their own. Because each sentence yields a finite set of results, the approach also gives a principled answer to when inference should stop.

## Key points
- Presuppositions come from two sources: lexical items such as *stop*, *manage*, *fail*, *force* and *appreciate*, and syntactic constructs such as cleft sentences and *only*.
- The worked examples show the scheme in action:
  - *John forced us to leave* entails *We left* through an identity transformation on a subformula.
  - *John stopped beating Mary* presupposes *John had been beating Mary*, which requires a non-trivial transformation.
- *manage* and *fail to* presuppose an attempt. Embedding under "is false" flips the entailment (*Dr Smith challenged John*) but leaves the presupposition (*attempted to challenge*) in place.
- The system sorts its output into three groups: non-NP presuppositions, NP-related presuppositions (each referent exists in the shared information), and entailments. Each result is shown both as a formula and as a regenerated English sentence.
- Embedded contexts are handled. Under *if…then*, presuppositions come out conditionalized. Under *says that*, they are wrapped in the speaker's claim. Full details are in Weischedel (1976).

## Interesting ideas
- Store inference triggers in the lexicon as small tree rewrites applied to a subformula. Inference then becomes local, explainable and cheap instead of open-ended theorem proving.
- Use survival under negation as the operational test separating presupposition from plain entailment.
- Inference stops naturally because each sentence licenses only a finite set of structurally derived consequences.
- NP-related presuppositions treat each referent as existing in the shared information, much like "given information".
- Every derived formula is regenerated into English, so each inference can be inspected as a sentence.

## For Mova

How these ideas could serve Mova, our small open language model — its files, stages and tests:

- **I1** (frames): verbs like *stop*, *manage*, *fail*, *force* could carry rewrite rules over their frame arguments, so prag emits presuppositions and entailments with a traceable rule ID.
- **I2** (learn): generate negated variants of silver sentences and use them as negative controls, checking that inferred presuppositions persist while plain entailments flip.
- **I3** (world): the world builder could restrict automatic state updates to these bounded sets, which avoids runaway chaining when populating entities and events.
- **I4** (world): definite NPs could add existence assertions to the text world, and coreference could check them against prior discourse.
- **I5** (back): verbalizing each inferred graph fact through the generator would give a human-readable audit of the inferences, plus a round-trip check.

*Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.*

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## Cite

Cite as: Aravind K. Joshi and Ralph Weischedel. 1977. Computation of a Subclass of Inferences: Presupposition and Entailment. eScholarship (California Digital Library).

The paper itself, not this page. BibTeX from the library's record of the work.

```bibtex
@inproceedings{joshi1977computation,
  title = {{Computation of a Subclass of Inferences: Presupposition and Entailment}},
  author = {Aravind K. Joshi and Ralph Weischedel},
  booktitle = {eScholarship (California Digital Library)},
  year = {1977},
  url = {https://aclanthology.org/J77-1008/}
}
```

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## References

23 references, 0 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet.

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*Updated 1 November 2026*