Natural Language Reasoning

with a Natural Theorem Prover

with a Natural Theorem Prover

Lecturer:
Lasha Abzianidze

Abstract

Natural language reasoning is a complex task that requires understanding the meanings of natural language expressions and recognizing semantic relations between them. The course is built around this highly interdisciplinary task. It introduces a computational theory of reasoning, called Natural Tableau, that combines the idea of a Natural Logic (logic using natural language as its vehicle of reasoning) with the semantic tableau method (a proof calculus that searches for certain situations).

The course not only introduces the theory of Natural Tableau but also shows its practical applications. In particular, we will show how an automated theorem prover, called LangPro, based on Natural Tableau, is used for Recognizing Textual Entailment (RTE) benchmarks. To overcome the knowledge sparsity and boost its performance, LangPro uses abductive reasoning to learn lexical relations from RTE training data.

Moreover, it will be also demonstrated how the prover can be extended for other languages than English, namely, for Dutch. During the course, attendees will also have the opportunity to run LangPro on RTE problems and examine human-readable proofs.

Schedule

Day 1

Day 2

Day 3

Day 4

Tableau-based theorem proving for natural logic and natural language; results on FraCaS dataset.

Day 5

Evaluation on SICK; learning as abduction; going beyond English (Dutch NLI)

References

- Abzianidze, L., Kogkalidis, K. (2021):
*A Logic-Based Framework for Natural Language Inference in Dutch*. CLIN, vol 11. - Abzianidze, L. (2020):
*Learning as Abduction: Trainable Natural Logic Theorem Prover for Natural Language Inference*. *SEM. - Abzianidze, L. (2017):
*LangPro: Natural Language Theorem Prover*. EMNLP. - Abzianidze, L. (2016):
*Natural Solution to FraCaS Entailment Problems*. *SEM. - Abzianidze, L. (2015):
*A Tableau Prover for Natural Logic and Language*. EMNLP. - Muskens, R. (2010):
*An Analytic Tableau System for Natural Logic*. LNCS, Springer. - LangPro: GitHub repository; online demo