The omega-inequality problem for concatenation hierarchies of star-free languages
Almeida, J., Klíma, O., Kunc, M. · Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) · 2016
The problem considered in this paper is whether an inequality of omega-terms is valid in a given level of a concatenation hierarchy of star-free languages. The main result shows that this problem is decidable for all (integer and half) levels of the Straubing-Thérien hierarchy.