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Hidden Schema Networks

Ramses Sanchez, Lukas Conrads, Pascal Welke, Kostadin Cvejoski, Cesar Ojeda Marin


Abstract
Large, pretrained language models infer powerful representations that encode rich semantic and syntactic content, albeit implicitly. In this work we introduce a novel neural language model that enforces, via inductive biases, explicit relational structures which allow for compositionality onto the output representations of pretrained language models. Specifically, the model encodes sentences into sequences of symbols (composed representations), which correspond to the nodes visited by biased random walkers on a global latent graph, and infers the posterior distribution of the latter. We first demonstrate that the model is able to uncover ground-truth graphs from artificially generated datasets of random token sequences. Next, we leverage pretrained BERT and GPT-2 language models as encoder and decoder, respectively, to infer networks of symbols (schemata) from natural language datasets. Our experiments show that (i) the inferred symbols can be interpreted as encoding different aspects of language, as e.g. topics or sentiments, and that (ii) GPT-2-like models can effectively be conditioned on symbolic representations. Finally, we explore training autoregressive, random walk “reasoning” models on schema networks inferred from commonsense knowledge databases, and using the sampled paths to enhance the performance of pretrained language models on commonsense If-Then reasoning tasks.
Anthology ID:
2023.acl-long.263
Volume:
Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
July
Year:
2023
Address:
Toronto, Canada
Editors:
Anna Rogers, Jordan Boyd-Graber, Naoaki Okazaki
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
4764–4798
Language:
URL:
https://aclanthology.org/2023.acl-long.263
DOI:
10.18653/v1/2023.acl-long.263
Bibkey:
Cite (ACL):
Ramses Sanchez, Lukas Conrads, Pascal Welke, Kostadin Cvejoski, and Cesar Ojeda Marin. 2023. Hidden Schema Networks. In Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 4764–4798, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
Hidden Schema Networks (Sanchez et al., ACL 2023)
Copy Citation:
PDF:
https://aclanthology.org/2023.acl-long.263.pdf
Video:
 https://aclanthology.org/2023.acl-long.263.mp4