Extracting Subregular constraints from Regular stringsets
Keywords:regular languages, finite-state automata, local languages, piecewise languages
We introduce algorithms that, given a Finite-State Automaton (FSA), compute a minimal set of forbidden local factors that define a Strictly Local (SL) tight approximation of the stringset recognised by the FSA and the set of forbidden piecewise factors that define a Strictly Piecewise (SP) tight approximation of that stringset, as well as a set of co-SL factors that, together with the SL and SP factors provide a set of purely conjunctive literal constraints defining a minimal superset of the stringset recognised by the automaton.
Using these, we have built computational tools that have allowed us to reproduce, by nearly purely computational means, the work of Rogers and his co-workers (Rogers et al. 2012) in which, using a mix of computational and analytical techniques, they completely characterised, with respect to the Local and Piecewise Subregular hierarchies, the constraints on the distribution of stress in human languages that are documented in the StressTyp2 database.
Our focus, in this paper, is on the algorithms and the method of their application. The phonology of stress patterns is a particularly good domain of application since, as we show here, they generally fall at the very lowest levels of complexity. We discuss these phonological results here, but do not consider their consequences in depth.
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