The task Task: Map a finite string α over an infinite alphabet onto a finite word w over a binary alphabet such that w reflects the structure of α "optimally".
We study the expressiveness and the complexity of static analysis of extended conjunctive regular path queries (ECRPQs), introduced by Barceló et al. (PODS '10). ECRPQs are an extension of con-junctive regular path queries (CRPQs), a well-studied language for querying graph structured databases. Our first main result shows that query containment and… (More)
Most modern implementations of regular expression engines allow the use of variables (also called backreferences). The resulting extended regular expressions (which, in the literature, are also called practical regular expressions, rewbr, or regex) are able to express non-regular languages. The present paper demonstrates that extended regular-expressions… (More)
We study the problem of generalizing from a finite sample to a language taken from a predefined language class. The two language classes we consider are subsets of the regular languages and have significance in the specification of XML documents (the classes corresponding to so called <i>chain regular expressions</i>, Chares, and to <i>single occurrence… (More)
• This is the author's version of a work that was accepted for publication in the journal, Theoretical Computer Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it… (More)
We study the inclusion problems for pattern languages that are generated by patterns with a bounded number of variables. This continues the work by Frey-denberger and Reidenbach (Information and Computation 208 (2010)) by showing that restricting the inclusion problem to significantly more restricted classes of patterns preserves undecidability, at least… (More)
We examine document spanners, a formal framework for information extraction that was introduced by Fagin et al. (PODS 2013). A document spanner is a function that maps an input string to a relation over spans (intervals of positions of the string). We focus on document spanners that are defined by regex formulas, which are basically regular expressions that… (More)