Kufleitner, ManfredLauser, Alexander2011-07-272016-03-312011-07-272016-03-312011381926303http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-64741http://elib.uni-stuttgart.de/handle/11682/2722http://dx.doi.org/10.18419/opus-2705The dot-depth hierarchy is a classification of star-free languages. It is related to the quantifier alternation hierarchy of first-order logic over finite words. We consider fragments of languages with dot-depth 1/2 and dot-depth 1 obtained by prohibiting the specification of prefixes or suffixes. As it turns out, these language classes are in one-to-one correspondence with fragments of existential first-order logic without min- or max-predicate. For all fragments, we obtain effective algebraic characterizations. Moreover, we give new combinatorial proofs for the decidability of the membership problem for dot-depth 1/2 and dot-depth 1.eninfo:eu-repo/semantics/openAccess004finite semigroups , dot-depth , regular languages , first-order logicworkingPaper2013-06-26