Conceitos essenciais
The languages of higher-dimensional automata (HDAs) are precisely the subsumption closures of monadic second-order (MSO) definable sets of interval ipomsets of bounded width.
Resumo
The paper studies higher-dimensional automata (HDAs) from a logical perspective. The key insights are:
- Languages of HDAs are sets of finite bounded-width interval pomsets with interfaces (iiPoms≤k) that are closed under order extension (subsumption).
- These languages are shown to be MSO-definable. Conversely, the order extensions of MSO-definable sets of iiPoms≤k are also languages of HDAs.
- As a consequence, unlike the case of all pomsets, order extension of MSO-definable sets of iiPoms≤k is also MSO-definable.
- The proof proceeds by establishing a correspondence between HDAs and MSO. The HDA-to-MSO direction uses a canonical sparse step decomposition of interval ipomsets, while the MSO-to-HDA direction relies on a connection between regular languages of interval ipomsets and regular languages of step decompositions.
- The results imply that the MSO theory of iiPoms≤k and the MSO model-checking problem for HDAs are decidable.