---
title: "An Efficient Easily Adaptable System for Interpreting Natural"
description: "Warren and Pereira present Chat-80, a prototype question answering system for a deliberately… 25 references, cited by 33 papers here."
authors: ["David H.D. Warren", "Fernando C.N. Pereira"]
year: 1982
venue: "Computational Linguistics"
source: "https://aclanthology.org/J82-3002/"
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/warren-1982-efficient-easily-adaptable-system-interpreting/"
---
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# An Efficient Easily Adaptable System for Interpreting Natural Language Queries

**Authors:** David H.D. Warren and [Fernando C.N. Pereira](https://md.research.elamur.ai/free/en/authors/fernando-pereira/) · **Year:** 1982 · **Venue:** [Computational Linguistics](https://md.research.elamur.ai/free/en/venues/cl/) ([Computational Linguistics 1982](https://md.research.elamur.ai/free/en/venues/cl/1982/)) · **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/J82-3002/) · [PDF](https://aclanthology.org/J82-3002.pdf) · [OpenAlex](https://openalex.org/W2164155814)

**Citations:** 275 citations (OpenAlex, 2026-10-14) · [33](https://md.research.elamur.ai/free/en/papers/warren-1982-efficient-easily-adaptable-system-interpreting/cited-by/) in our library, of the 149,439 papers whose bibliographies we read

## Summary
Practical natural language interfaces to databases need two things: fast answers and easy transfer to new domains. Warren and Pereira present Chat-80, a prototype question answering system for a deliberately restricted English subset, written entirely in Prolog. It extends earlier work by Dahl (a Spanish system) and Colmerauer. Questions are parsed with extraposition grammars (XGs) and translated into the Prolog subset of first-order logic. Determiners become standard quantifiers rather than Colmerauer's three-branched quantifiers (3BQs), and presuppositions are deliberately ignored. A planning stage then restructures the logical form, much like query optimisation in relational databases, and the resulting Prolog code is executed to obtain the answer. On a world geography database, most single-sentence queries, including fairly complex ones, need far less than a second of CPU time to answer. The authors find that answering, not parsing, dominates processing cost. They argue that storing domain knowledge as separate declarative data makes the system easier to adapt than procedural designs such as LUNAR.

## Key points
- Chat-80 has three stages: English is translated into logic, planning turns the logic into efficient Prolog, and execution produces the answer. It runs under DEC-10 Prolog.
- The test database covers more than 150 countries, plus oceans, major seas, rivers and cities. The largest relation, `borders`, holds over 850 tuples.
- System sizes in Prolog clauses and DEC-10 words:
  - NL analysis: about 580 clauses, 24,000 words.
  - Planning and execution: about 290 clauses, 8,500 words.
  - Geographical vocabulary: about 180 clauses, 4,000 words.
  - Geographical database: about 1,590 clauses, 22,500 words.
  - Roughly 50 additional words are domain independent.
- Compared with the original Chat (based on metamorphosis grammars), Chat-80 changes several things:
  - It uses new determiner semantics and scoping rules.
  - It adds query planning.
  - It covers more of English.
  - It performs analysis in three separate phases.
- Natural language analysis takes only a small share of total time for non-trivial queries. Extending the vocabulary barely affects speed because the dictionary is indexed.

*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: David H.D. Warren and Fernando C.N. Pereira. 1982. An Efficient Easily Adaptable System for Interpreting Natural Language Queries. Computational Linguistics.

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

```bibtex
@article{warren1982efficient,
  title = {{An Efficient Easily Adaptable System for Interpreting Natural Language Queries}},
  author = {David H.D. Warren and Fernando C.N. Pereira},
  journal = {Computational Linguistics},
  year = {1982},
  doi = {10.5555/972942.972944},
  url = {https://doi.org/10.5555/972942.972944}
}
```

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## References

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

1. Burton, R.R. 1976 Semantic grammar: an engineering technique for constructing natural language understanding systems. Report 3453. Bolt Beranek and Newman Inc. (December). [find](https://scholar.google.com/scholar?q=Burton%2C+R%2ER%2E+1976+Semantic+grammar%3A+an+engineering+technique+for+constructing+natural+language+understanding+systems%2E+Report+3453%2E+Bolt+Beranek+and+Newman+Inc%2E+%28December%29%2E)
2. Byrd, L., Pereira, F., and Warren, D.H.D. 1980 A guide to version 3 of DEC-10 Prolog. Occasional Paper 19. Dept. of Artificial Intelligence, University of Edinburgh (July). [find](https://scholar.google.com/scholar?q=Byrd%2C+L%2E%2C+Pereira%2C+F%2E%2C+and+Warren%2C+D%2EH%2ED%2E+1980+A+guide+to+version+3+of+DEC%2D10+Prolog%2E+Occasional+Paper+19%2E+Dept%2E+of+Artificial+Intelligence%2C+University+of+Edinburgh+%28July%29%2E)
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11. Pereira, F.C.N. 1982 Logic for natural language analysis. Ph.D. thesis. University of Edinburgh. [find](https://scholar.google.com/scholar?q=Pereira%2C+F%2EC%2EN%2E+1982+Logic+for+natural+language+analysis%2E+Ph%2ED%2E+thesis%2E+University+of+Edinburgh%2E)
12. Pereira, F.C.N. and Warren, D.H.D. 1980 Definite clause grammars for language analysis - a survey of the formalism and a comparison with augmented transition networks. Artificial Intelligence 13, 231-278. [find](https://scholar.google.com/scholar?q=Pereira%2C+F%2EC%2EN%2E+and+Warren%2C+D%2EH%2ED%2E+1980+Definite+clause+grammars+for+language+analysis+%2D+a+survey+of+the+formalism+and+a+comparison+with+augmented+transition+networks%2E+Artificial+Intelligence+13%2C+231%2D)
13. Volume 8, Number 3-4, July-December 1982 [find](https://scholar.google.com/scholar?q=Volume+8%2C+Number+3%2D4%2C+July%2DDecember+1982)
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15. Roussel, P. 1975 Prolog: manuel de reference et d'utilisation Group d'Intelligence Artificielle, UER de Luminy, Universit6 d'Aix-Marseille II. [find](https://scholar.google.com/scholar?q=Roussel%2C+P%2E+1975+Prolog%3A+manuel+de+reference+et+d%27utilisation+Group+d%27Intelligence+Artificielle%2C+UER+de+Luminy%2C+Universit6+d%27Aix%2DMarseille+II%2E)
16. Stonebraker, M., Wong, E., Kreps, P. and Held, G. 1976 The design and implementation of INGRES. A C M Trans. on Database Systems 1, 3 (Sept.) 189-222. [find](https://scholar.google.com/scholar?q=Stonebraker%2C+M%2E%2C+Wong%2C+E%2E%2C+Kreps%2C+P%2E+and+Held%2C+G%2E+1976+The+design+and+implementation+of+INGRES%2E+A+C+M+Trans%2E+on+Database+Systems+1%2C+3+%28Sept%2E%29+189%2D222%2E)
17. Vanlehn, K.A. 1978 Determining the Scope of English Quantifiers. Master's thesis. Published as Report AI-TR-483. M.I.T. (June). [find](https://scholar.google.com/scholar?q=Vanlehn%2C+K%2EA%2E+1978+Determining+the+Scope+of+English+Quantifiers%2E+Master%27s+thesis%2E+Published+as+Report+AI%2DTR%2D483%2E+M%2EI%2ET%2E+%28June%29%2E)
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19. Warren, D.H.D. 1979 Prolog on the DECsystem-10. In Michie, D., Ed., Expert Systems in the Micro-Electronic Age. Edinburgh University Press. [find](https://scholar.google.com/scholar?q=Warren%2C+D%2EH%2ED%2E+1979+Prolog+on+the+DECsystem%2D10%2E+In+Michie%2C+D%2E%2C+Ed%2E%2C+Expert+Systems+in+the+Micro%2DElectronic+Age%2E+Edinburgh+University+Press%2E)
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*Updated 29 October 2026*