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The separability problem for regular languages asks, given two regular languages I and E, whether there exists a language S that separates the two, that is, includes I but contains nothing from E. Typically, S comes from a simple, less expressive class of languages than I and E. In general, a simple separator $S$ can be seen as an approximation of I or as an explanation of how I and E are different. In a database context, separators can be used for explaining the result of regular path queries or for finding explanations for the difference between paths in a graph database, that is, how paths from given nodes u_1 to v_1 are different from those from u_2 to v_2. We study the complexity of separability of regular languages by combinations of subsequences or subwords of a given length k. The rationale is that the parameter k can be used to influence the size and simplicity of the separator. The emphasis of our study is on tracing the tractability of the problem.
@InProceedings{hofman_et_al:LIPIcs.ICDT.2015.230,
author = {Hofman, Piotr and Martens, Wim},
title = {{Separability by Short Subsequences and Subwords}},
booktitle = {18th International Conference on Database Theory (ICDT 2015)},
pages = {230--246},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-939897-79-8},
ISSN = {1868-8969},
year = {2015},
volume = {31},
editor = {Arenas, Marcelo and Ugarte, Mart{\'\i}n},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2015.230},
URN = {urn:nbn:de:0030-drops-49878},
doi = {10.4230/LIPIcs.ICDT.2015.230},
annote = {Keywords: separability, complexity, graph data, debugging}
}