We propose a novel approach to minimization of deterministic finite automata (DFA), in which the DFA is further minimized at the expense of relaxing equality of languages to merely a similarity. As the notion of similarity of languages, we consider the edit distance between languages ℒ, ℒ', i.e., the minimal number of edits necessary to transform any word from ℒ to some word from ℒ' and vice versa. In this paper we address two problems: minimization up to a predetermined edit distance given in the input, and minimization up to a bounded edit distance, in which there has to be an upper bound on the number of edits, but it is not specified. We show the first problem to be PSpace {}-complete and that the second problem is in Σ₂^p, and both NP-hard and coNP-hard. We show that if we limit how many strongly connected components can be visited by a single run (i.e., bounded SCC-depth), the problem becomes NP-complete. We also establish maximal subclasses of DFA over which minimization up to a bounded edit distance can be performed in polynomial time. Additionally, we provide a succinct overview of alternative metrics for assessing language similarity.
@InProceedings{michaliszyn_et_al:LIPIcs.MFCS.2025.77, author = {Michaliszyn, Jakub and Otop, Jan}, title = {{Minimization of Deterministic Finite Automata Modulo the Edit Distance}}, booktitle = {50th International Symposium on Mathematical Foundations of Computer Science (MFCS 2025)}, pages = {77:1--77:17}, 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.2025.77}, URN = {urn:nbn:de:0030-drops-241843}, doi = {10.4230/LIPIcs.MFCS.2025.77}, annote = {Keywords: automata theory, automata minimization, edit distance} }
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