Visibly Pushdown Languages (VPLs), recognized by Visibly Pushdown Automata (VPAs), are a nicely behaved family of contextfree languages. It has been shown that VPAs are equivalent ...
We close affirmatively a question which has been open for long time: decidability of the HOM problem. The HOM problem consists in determining, given a tree homomorphism D and a re...
Guillem Godoy, Omer Giménez, Lander Ramos and Car...
Abstract. Based on the recursion mechanism of the XML transformation language XSL, the document transformation language DTL is defined. First the instantiation DTLreg is considere...
Abstract. We give a general framework for approximate query processing in semistructured databases. We focus on regular path queries, which are the integral part of most of the que...