A Refutation of Finite-State Language Models through Zipf’s Law for Factual Knowledge

Autor: Łukasz Dębowski
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Entropy, Vol 23, Iss 9, p 1148 (2021)
Druh dokumentu: article
ISSN: 1099-4300
DOI: 10.3390/e23091148
Popis: We present a hypothetical argument against finite-state processes in statistical language modeling that is based on semantics rather than syntax. In this theoretical model, we suppose that the semantic properties of texts in a natural language could be approximately captured by a recently introduced concept of a perigraphic process. Perigraphic processes are a class of stochastic processes that satisfy a Zipf-law accumulation of a subset of factual knowledge, which is time-independent, compressed, and effectively inferrable from the process. We show that the classes of finite-state processes and of perigraphic processes are disjoint, and we present a new simple example of perigraphic processes over a finite alphabet called Oracle processes. The disjointness result makes use of the Hilberg condition, i.e., the almost sure power-law growth of algorithmic mutual information. Using a strongly consistent estimator of the number of hidden states, we show that finite-state processes do not satisfy the Hilberg condition whereas Oracle processes satisfy the Hilberg condition via the data-processing inequality. We discuss the relevance of these mathematical results for theoretical and computational linguistics.
Databáze: Directory of Open Access Journals
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