We construct an algorithm that inputs an MSO-interpretation from finite words to graphs, and decides if there exists a k ∈ ℕ such that the class of graphs induced by the interpretation is not well-quasi-ordered by the induced subgraph relation when vertices are freely labelled using {1, …, k}. In case no such k exists, we also prove that the class of graphs is not well-quasi-ordered by the induced subgraph relation when vertices are freely labelled using any well-quasi-ordered set of labels. As a byproduct of our analysis, we prove that for classes of bounded linear clique-width, a weak version of a conjecture by Pouzet holds.
@InProceedings{lopez:LIPIcs.MFCS.2025.70, author = {Lopez, Aliaume}, title = {{Labelled Well Quasi Ordered Classes of Bounded Linear Clique-Width}}, booktitle = {50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)}, pages = {70:1--70:17}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-388-1}, ISSN = {1868-8969}, year = {2025}, volume = {345}, editor = {Gawrychowski, Pawe{\l} and Mazowiecki, Filip and Skrzypczak, Micha{\l}}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2025.70}, URN = {urn:nbn:de:0030-drops-241773}, doi = {10.4230/LIPIcs.MFCS.2025.70}, annote = {Keywords: well-quasi-ordering, linear clique-width, MSO transduction, automata theory} }
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