A note on the commutative closure of star-free languages
Information Processing Letters
Languages, automata, and logic
Handbook of formal languages, vol. 3
Polynomial Operations on Rational Languages
STACS '87 Proceedings of the 4th Annual Symposium on Theoretical Aspects of Computer Science
Extrapolating Tree Transformations
CAV '02 Proceedings of the 14th International Conference on Computer Aided Verification
Reachability Analysis over Term Rewriting Systems
Journal of Automated Reasoning
Permutation rewriting and algorithmic verification
Information and Computation
Hi-index | 0.89 |
A recent paper by Bouajjani, Muscholl and Touili shows that the class of languages accepted by partially ordered word automata (or equivalently accepted by @S"2-formulae) is closed under semi-commutation and it suggested the following open question: can we extend this result to tree languages? This problem can be addressed by proving (1) that the class of tree regular languages accepted by @S"2 formulae is strictly included in the class of languages accepted by partially ordered automata, and (2) that Bouajjani and the others results cannot be extended to tree.