The generating power of weighted tree automata with initial algebra semantics

Fuente: arXiv
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Main Authors: Droste, Manfred, Fülöp, Zoltán, Tepavčević, Andreja, Vogler, Heiko
Format: Preprint
Published: 2024
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author Droste, Manfred
Fülöp, Zoltán
Tepavčević, Andreja
Vogler, Heiko
author_facet Droste, Manfred
Fülöp, Zoltán
Tepavčević, Andreja
Vogler, Heiko
contents We consider the images of the initial algebra semantics of weighted tree automata over strong bimonoids (hence also over semirings). These images are subsets of the carrier set of the underlying strong bimonoid. We consider locally finite, weakly locally finite, and bi-locally finite strong bimonoids. We show that there exists a strong bimonoid which is weakly locally finite and not locally finite. We also show that if the ranked alphabet contains a binary symbol, then for any finitely generated strong bimonoid, weighted tree automata can generate, via their initial algebra semantics, all elements of the strong bimonoid. As a consequence of these results, for weakly locally finite strong bimonoids which are not locally finite, weighted tree automata can generate infinite images provided that the input ranked alphabet contains at least one binary symbol. This is in sharp contrast to the setting of weighted string automata, where each such image is known to be finite. As a further consequence, for any finitely generated semiring, there exists a weighted tree automaton which generates, via its run semantics, all elements of the semiring.
format Preprint
id arxiv_https___arxiv_org_abs_2405_20753
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The generating power of weighted tree automata with initial algebra semantics
Droste, Manfred
Fülöp, Zoltán
Tepavčević, Andreja
Vogler, Heiko
Formal Languages and Automata Theory
68Q45, 03D05 (Primary), 68R99 (Secondary)
We consider the images of the initial algebra semantics of weighted tree automata over strong bimonoids (hence also over semirings). These images are subsets of the carrier set of the underlying strong bimonoid. We consider locally finite, weakly locally finite, and bi-locally finite strong bimonoids. We show that there exists a strong bimonoid which is weakly locally finite and not locally finite. We also show that if the ranked alphabet contains a binary symbol, then for any finitely generated strong bimonoid, weighted tree automata can generate, via their initial algebra semantics, all elements of the strong bimonoid. As a consequence of these results, for weakly locally finite strong bimonoids which are not locally finite, weighted tree automata can generate infinite images provided that the input ranked alphabet contains at least one binary symbol. This is in sharp contrast to the setting of weighted string automata, where each such image is known to be finite. As a further consequence, for any finitely generated semiring, there exists a weighted tree automaton which generates, via its run semantics, all elements of the semiring.
title The generating power of weighted tree automata with initial algebra semantics
topic Formal Languages and Automata Theory
68Q45, 03D05 (Primary), 68R99 (Secondary)
url https://arxiv.org/abs/2405.20753