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@article{925216, author = {Klíma, Ondřej and Polák, Libor}, article_location = {Singapur}, article_number = {4}, keywords = {varieties of languages; piecewise testable languages; syntactic monoid}, language = {eng}, issn = {0129-0541}, journal = {International Journal of Foundations of Computer Science}, title = {Hierarchies of piecewise testable languages}, volume = {21}, year = {2010} }
TY - JOUR ID - 925216 AU - Klíma, Ondřej - Polák, Libor PY - 2010 TI - Hierarchies of piecewise testable languages JF - International Journal of Foundations of Computer Science VL - 21 IS - 4 SP - 517-533 EP - 517-533 PB - World Scientific SN - 01290541 KW - varieties of languages KW - piecewise testable languages KW - syntactic monoid N2 - The classes of languages which are Boolean combinations of languages of the form A*(a1)A*(a2)A*... A*(am)A*, where a1,...,am are letters, with k>m, for a fixed k > 0, form a natural hierarchy within piecewise testable languages and have been studied by Simon, Blanchet-Sadri, Volkov and others. The main issues were the existence of finite bases of identities for the corresponding pseudovarieties of monoids and monoids generating these pseudovarieties. Here we deal with similar questions concerning the finite unions and positive Boolean combinations of the languages of the form above. In the first case the corresponding pseudovarieties are given by a single identity, in the second case there are finite bases for k equals to 1 and 2 and there is no finite basis for k >3 (the case k = 3 remains open). All the pseudovarieties are generated by a single algebraic structure. ER -
KLÍMA, Ondřej a Libor POLÁK. Hierarchies of piecewise testable languages. \textit{International Journal of Foundations of Computer Science}. Singapur: World Scientific, 2010, roč.~21, č.~4, s.~517-533. ISSN~0129-0541.
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