---
title: "Responding Intelligently to Unparsable Inputs — Weischedel 1980"
description: "They propose three techniques, each implemented in one of two systems: a tutor for German reading… 27 references, cited by 16 papers here."
authors: ["Ralph M. Weischedel", "John E. Black"]
year: 1980
venue: "Computational Linguistics"
source: "https://aclanthology.org/J80-2003/"
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/weischedel-1980-responding-intelligently-unparsable-inputs/"
---
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# Responding Intelligently to Unparsable Inputs

**Authors:** [Ralph M. Weischedel](https://md.research.elamur.ai/free/en/authors/ralph-weischedel/) and John E. Black · **Year:** 1980 · **Venue:** [Computational Linguistics](https://md.research.elamur.ai/free/en/venues/cl/) ([Computational Linguistics 1980](https://md.research.elamur.ai/free/en/venues/cl/1980/)) · **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/J80-2003/) · [PDF](https://aclanthology.org/J80-2003.pdf) · [OpenAlex](https://openalex.org/W1574247107)

**Citations:** 59 citations (OpenAlex, 2026-10-14) · [16](https://md.research.elamur.ai/free/en/papers/weischedel-1980-responding-intelligently-unparsable-inputs/cited-by/) in our library, of the 149,439 papers whose bibliographies we read

## Summary
Practical natural language interfaces, such as database front ends, consultation programs and office tools, will inevitably receive inputs outside their coverage. The authors argue that such a system must tell users precisely why an input failed so they can reformulate it. They propose three techniques, each implemented in one of two systems: a tutor for German reading comprehension and a system that computes presuppositions and entailments.

1. **Presupposition checking.** The system verifies the given information of an input against its world model and reports any assumption that does not hold.
2. **Relaxation of tests during parsing.** Grammar constraints are loosened so that ill-formed sentences can still be translated and the violation can be flagged.
3. **Heuristics for failed parses.** When no parse exists, the system uses the expectations of a top-down, left-to-right parser to describe where and why it got stuck.

The methods diagnose problems but do not propose rephrasings. The work matters because helpful failure feedback is presented as a precondition for non-programmers to accept natural language systems.

## Key points
- **Motivating example.** Woods's lunar rock question about "all your samples" broke the system in three ways:
  - Syntax: a predeterminer before a determiner was not covered.
  - Semantics: there were no rules or data for sample weight.
  - Pragmatics: the system was never modelled as owning the samples.
- **Psychological basis.** Presupposition handling draws on Clark and Haviland's given/new model. The system checks given information in context before asserting new information, and the computation is organized in an augmented transition network (ATN) and lexicon.
- **Error diagnosis in the German tutor.**
  - It catches misunderstood questions when the answer does not entail the question's given information.
  - It reports definite noun phrases that refer to nothing.
  - It catches misused words, such as *essen* (human eater) versus *fressen* (animal eater).
- **Anticipated mistakes.** Common learner errors are encoded as explicit ATN paths that both translate the answer and generate a correction message. An example is a past participle not placed at the end of the clause ("Ich habe gegessen das Fleisch").
- **Related work.** Kaplan (1977, 1979) extended presupposition-based cooperative responses to database queries that would return empty answers.

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

## Institutions

- [University of Delaware](https://md.research.elamur.ai/free/en/universities/university-of-delaware/) — University, Newark, United States · 20 works · 1,056 citations

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🧭 Topics (1): [😉 Implicature](https://md.research.elamur.ai/free/en/topics/implicature/) · 138 works

## Cite

Cite as: Ralph M. Weischedel and John E. Black. 1980. Responding Intelligently to Unparsable Inputs. Computational Linguistics.

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

```bibtex
@article{weischedel1980responding,
  title = {{Responding Intelligently to Unparsable Inputs}},
  author = {Ralph M. Weischedel and John E. Black},
  journal = {Computational Linguistics},
  year = {1980},
  doi = {10.5555/972439.972442},
  url = {https://doi.org/10.5555/972439.972442}
}
```

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## References

27 references, 1 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet.

1. Allen, James F., "A Plan-Based Approach to Speech Act Recognition," Ph.D. Thesis, Dept. of Computer Science, University of Toronto, Toronto, Canada, 1979. [find](https://scholar.google.com/scholar?q=Allen%2C+James+F%2E%2C+%22A+Plan%2DBased+Approach+to+Speech+Act+Recognition%2C%22+Ph%2ED%2E+Thesis%2C+Dept%2E+of+Computer+Science%2C+University+of+Toronto%2C+Toronto%2C+Canada%2C+1979%2E)
2. Anderson, Barbara B., "TransformationaUy Based English Strings and their Word Subclasses," String Program Reports No. 7, Linguistic String Program, New York University, New York, NY 1970. [find](https://scholar.google.com/scholar?q=Anderson%2C+Barbara+B%2E%2C+%22TransformationaUy+Based+English+Strings+and+their+Word+Subclasses%2C%22+String+Program+Reports+No%2E+7%2C+Linguistic+String+Program%2C+New+York+University%2C+New+York%2C+NY+1970%2E)
3. Bobrow, D. G., R. M. Kaplan, M. Kay, D. A. Norman, H. Thompson, and T. Winograd, "GUS, A Frame Driven Dialog System," Artificial Intelligence 8, 2, 1977. [find](https://scholar.google.com/scholar?q=Bobrow%2C+D%2E+G%2E%2C+R%2E+M%2E+Kaplan%2C+M%2E+Kay%2C+D%2E+A%2E+Norman%2C+H%2E+Thompson%2C+and+T%2E+Winograd%2C+%22GUS%2C+A+Frame+Driven+Dialog+System%2C%22+Artificial+Intelligence+8%2C+2%2C+1977%2E)
4. Bobrow, Robert J., "The RUS System," in B. L. Webber and R. Bobrow, Research in Natural Language Understanding, BBN Report 3878, Bolt Beranek and Newman Inc., Cambridge, MA, 1978. [find](https://scholar.google.com/scholar?q=Bobrow%2C+Robert+J%2E%2C+%22The+RUS+System%2C%22+in+B%2E+L%2E+Webber+and+R%2E+Bobrow%2C+Research+in+Natural+Language+Understanding%2C+BBN+Report+3878%2C+Bolt+Beranek+and+Newman+Inc%2E%2C+Cambridge%2C+MA%2C+1978%2E)
5. Brown, J. S. and R. R. Burton, "Multiple Representations of Knowledge for Tutorial Reasoning." In D. G. Bobrow and A. Collins, Eds., Representation and Understanding, New York: Academic Press, 1975. [find](https://scholar.google.com/scholar?q=Brown%2C+J%2E+S%2E+and+R%2E+R%2E+Burton%2C+%22Multiple+Representations+of+Knowledge+for+Tutorial+Reasoning%2E%22+In+D%2E+G%2E+Bobrow+and+A%2E+Collins%2C+Eds%2E%2C+Representation+and+Understanding%2C+New+York%3A+Academic+Press%2C+1975%2E)
6. Burton, R. R., "Semantic Grammar: An Engineering Technique for Construction of Natural Language Understanding Systems." BBN Report 3453, Bolt, Beranek, and Newman, Cambridge, Mass. Also, Ph.D. Dissertation, University of California, Irvine, CA, 1976. [find](https://scholar.google.com/scholar?q=Burton%2C+R%2E+R%2E%2C+%22Semantic+Grammar%3A+An+Engineering+Technique+for+Construction+of+Natural+Language+Understanding+Systems%2E%22+BBN+Report+3453%2C+Bolt%2C+Beranek%2C+and+Newman%2C+Cambridge%2C+Mass%2E+Also%2C+Ph%2ED%2E+Dissert)
7. Clark, Herbert H. and Susan E. Haviland, "Comprehension and the Given-New Contract. In R. Freedle, Ed., Discourse Processes: Advances in Research and Theory, Vol. 1. Discourse Production and Comprehension. Norwood, N J: Ablex Publishing Corporation, 1977. Codd, E. F., R. S. Arnold, J. M. Cadiou, C.… [find](https://scholar.google.com/scholar?q=Clark%2C+Herbert+H%2E+and+Susan+E%2E+Haviland%2C+%22Comprehension+and+the+Given%2DNew+Contract%2E+In+R%2E+Freedle%2C+Ed%2E%2C+Discourse+Processes%3A+Advances+in+Research+and+Theory%2C+Vol%2E+1%2E+Discourse+Production+and+Comprehen)
8. Floyd, R. W., "Assigning Meanings to Programs," Proc. of a Symposium in Applied Mathematics, Vol. 19. American Mathematical Society, 1967. Grishman, Ralph, "Implementation of the String Parser of English." In R. Rustin, Ed., Natural Language Processing. [find](https://scholar.google.com/scholar?q=Floyd%2C+R%2E+W%2E%2C+%22Assigning+Meanings+to+Programs%2C%22+Proc%2E+of+a+Symposium+in+Applied+Mathematics%2C+Vol%2E+19%2E+American+Mathematical+Society%2C+1967%2E+Grishman%2C+Ralph%2C+%22Implementation+of+the+String+Parser+of+Engl)
9. New York: Algorithmies Press, 1973. Haviland, Susan E. and Herbert H. Clark, "What's New? Acquiring new information as a process in comprehension." Journal of Verbal Learning and Verbal Behavior, 13, 1974. Hayes, P. and R. Reddy, "An Anatomy of Graceful Interaction in Spoken and Written Man-Machine… [find](https://scholar.google.com/scholar?q=New+York%3A+Algorithmies+Press%2C+1973%2E+Haviland%2C+Susan+E%2E+and+Herbert+H%2E+Clark%2C+%22What%27s+New%3F+Acquiring+new+information+as+a+process+in+comprehension%2E%22+Journal+of+Verbal+Learning+and+Verbal+Behavior%2C+13%2C+)
10. Kaplan, S. Jerrold, "[Indirect Responses to Loaded Questions](https://md.research.elamur.ai/free/en/papers/kaplan-1978-indirect-responses-loaded-questions/)," Theoretical Issues in Natural Language Processing-2, University of Illinois at Urbana-Champaign, July, 1978.
11. Kaplan, S. Jerrold, "Cooperative Responses from a Natural Language Data Base Query System, ') Ph.D. Dissertation, Dept. of Computer & Information Science, University of Pennsylvania, Philadelphia, PA, 1979. [find](https://scholar.google.com/scholar?q=Kaplan%2C+S%2E+Jerrold%2C+%22Cooperative+Responses+from+a+Natural+Language+Data+Base+Query+System%2C+%27%29+Ph%2ED%2E+Dissertation%2C+Dept%2E+of+Computer+%26+Information+Science%2C+University+of+Pennsylvania%2C+Philadelphia%2C+PA%2C)
12. Karttunen, L., "Presuppositions of Compound Sentences," Linguistic Inquiry, 4, 1973. [find](https://scholar.google.com/scholar?q=Karttunen%2C+L%2E%2C+%22Presuppositions+of+Compound+Sentences%2C%22+Linguistic+Inquiry%2C+4%2C+1973%2E)
13. Karttunen, L. and S. Peters, "Conventional Implieature in Montague Grammar," Proc. of the First Annual Meeting of the Berkeley Linguistics Society, Berkeley, CA, 1975 [find](https://scholar.google.com/scholar?q=Karttunen%2C+L%2E+and+S%2E+Peters%2C+%22Conventional+Implieature+in+Montague+Grammar%2C%22+Proc%2E+of+the+First+Annual+Meeting+of+the+Berkeley+Linguistics+Society%2C+Berkeley%2C+CA%2C+1975)
14. Kwasny, Stan and Norman K. Sondheimer, "Ungrammatieality and Extra-Grammaticality in Natural Language Understanding Systems," Proceedings of the 17th Annual Meeting of the Association for Computational Linguistics, 1979. [find](https://scholar.google.com/scholar?q=Kwasny%2C+Stan+and+Norman+K%2E+Sondheimer%2C+%22Ungrammatieality+and+Extra%2DGrammaticality+in+Natural+Language+Understanding+Systems%2C%22+Proceedings+of+the+17th+Annual+Meeting+of+the+Association+for+Computationa)
15. Levin, J. A. and J. A. Moore, "'Dialogue Games: Meta-communication Structures for Natural Language Interaction," Cognitive Science 1, 4, 1978. [find](https://scholar.google.com/scholar?q=Levin%2C+J%2E+A%2E+and+J%2E+A%2E+Moore%2C+%22%27Dialogue+Games%3A+Meta%2Dcommunication+Structures+for+Natural+Language+Interaction%2C%22+Cognitive+Science+1%2C+4%2C+1978%2E)
16. Mann, W. C., "Dialogue Games," in K. Hintikka, et.al., Eds., Models of Dialogue, Amsterdam: North-Holland Publishing Company, 1979. [find](https://scholar.google.com/scholar?q=Mann%2C+W%2E+C%2E%2C+%22Dialogue+Games%2C%22+in+K%2E+Hintikka%2C+et%2Eal%2E%2C+Eds%2E%2C+Models+of+Dialogue%2C+Amsterdam%3A+North%2DHolland+Publishing+Company%2C+1979%2E)
17. Mays, Eric, "Correcting Misconceptions About Data Base Structure," Proceedings of the Conference of the Canadian Society for Computational Studies of Intelligence, 1980. [find](https://scholar.google.com/scholar?q=Mays%2C+Eric%2C+%22Correcting+Misconceptions+About+Data+Base+Structure%2C%22+Proceedings+of+the+Conference+of+the+Canadian+Society+for+Computational+Studies+of+Intelligence%2C+1980%2E)
18. Oh, Choon-Kyu and David A. Dineen, (Eds.), Presupposition, Vol. 11, Syntax and Semantics, New York: Academic Press, 1979. [find](https://scholar.google.com/scholar?q=Oh%2C+Choon%2DKyu+and+David+A%2E+Dineen%2C+%28Eds%2E%29%2C+Presupposition%2C+Vol%2E+11%2C+Syntax+and+Semantics%2C+New+York%3A+Academic+Press%2C+1979%2E)
19. Sager, Naomi, "The String Parser for Scientific Literature." In R. Rustin, Ed., Natural Language Processing. New York: Algorithmies Press, 1973. [find](https://scholar.google.com/scholar?q=Sager%2C+Naomi%2C+%22The+String+Parser+for+Scientific+Literature%2E%22+In+R%2E+Rustin%2C+Ed%2E%2C+Natural+Language+Processing%2E+New+York%3A+Algorithmies+Press%2C+1973%2E)
20. Weischedel, Ralph M., "Computation of a Unique Subclass of Inferences: Presupposition and Entailment," Ph.D. Thesis, Department of Computer and Information Science, University of Pennsylvania, Philadelphia, PA, 1975. [find](https://scholar.google.com/scholar?q=Weischedel%2C+Ralph+M%2E%2C+%22Computation+of+a+Unique+Subclass+of+Inferences%3A+Presupposition+and+Entailment%2C%22+Ph%2ED%2E+Thesis%2C+Department+of+Computer+and+Information+Science%2C+University+of+Pennsylvania%2C+Philade)
21. Weischedel, Ralph M., "A New Semantic Computation While Parsing: Presupposition and Entailment." In C. Oh and D. Dineen, Eds., Presupposition, Vol. 11, Syntax and Semantics, New York: Academic Press, 1979. [find](https://scholar.google.com/scholar?q=Weischedel%2C+Ralph+M%2E%2C+%22A+New+Semantic+Computation+While+Parsing%3A+Presupposition+and+Entailment%2E%22+In+C%2E+Oh+and+D%2E+Dineen%2C+Eds%2E%2C+Presupposition%2C+Vol%2E+11%2C+Syntax+and+Semantics%2C+New+York%3A+Academic+Press%2C+)
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25. Woods, W. A., "An Experimental Parsing System for Transition Network Grammars." In R. Rustin, Ed., Natural Language Processing. New York: Algorithmics Press, 1973a. Woods, W. A., "Progress in natural language understanding -- An application to lunar geology,," AFIPS Conference Proceedings, NCC. [find](https://scholar.google.com/scholar?q=Woods%2C+W%2E+A%2E%2C+%22An+Experimental+Parsing+System+for+Transition+Network+Grammars%2E%22+In+R%2E+Rustin%2C+Ed%2E%2C+Natural+Language+Processing%2E+New+York%3A+Algorithmics+Press%2C+1973a%2E+Woods%2C+W%2E+A%2E%2C+%22Progress+in+natural+)
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*Updated 30 October 2026*