Abstract

This paper introduces a notion of equivalence for higher-dimensional automata, called weak equivalence. Weak equivalence focuses mainly on a traditional trace language and a new homology language, which captures the overall independence structure of an HDA. It is shown that weak equivalence is compatible with both the tensor product and the coproduct of HDAs and that, under certain conditions, HDAs may be reduced to weakly equivalent smaller ones by merging and collapsing cubes.

Highlights

  • 1.1 Higher-dimensional automataA higher-dimensional automaton (HDA) is an automaton with a supplementary structure consisting of two- and higher-dimensional cubes linking its states and transitions

  • As in the case of the trace language and the fundamental monoid, we show that the homology language is compatible with cubical dimaps and establish formulas to compute it for tensor products and coproducts

  • This paper introduced weak equivalence, a coarse notion of equivalence for higher-dimensional automata

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Summary

Higher-dimensional automata

We present basic material on precubical sets, concurrent alphabets, and higher-dimensional automata. The definition of higher-dimensional automata is essentially the one of van Glabbeek [Gla06], with the difference that we consider HDAs over concurrent alphabets and allow labels to be words. It is not our intention to provide a comprehensive introduction to the material of this section. Explanations, and examples, the reader is referred to, e.g., [Die, Maz, FGH+16, Gla06]

Weak equivalence
Weak implementation
Reduction of HDAs
Background and related work
Precubical sets
Tensor product of precubical sets
Precubical cubes
Dihomotopy
Free monoids
Concurrent alphabets
Trace monoids
2.10 Higher-dimensional automata
2.12 Tensor product of HDAs
2.13 Coproduct of HDAs
Cubical dimaps
Geometric realization
Cubical dimaps of precubical sets
Cubical dimaps and paths
Cubical dimaps of HDAs
The trace language of an HDA
Saturated safety properties
Trace language
The trace language of a tensor product
Fundamental monoid
The trace language of a coproduct
The homology language of an HDA
Chain complexes and homology
Cubical chains and cubical homology
The edge eix
Labeling chain map
Labeled homology
The homology language
The homology language of a tensor product
The homology language of a coproduct
5.10 Independence
Accessible HDAs
Coaccessible HDAs
Weak implementation and weak equivalence
Topological abstraction
Cube collapses
Cube merging
Example
Concluding remarks
Full Text
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