Given any dag t representing a fully or partially compressed XML document, we present a method for evaluating any positive unary query expressed in terms of Core XPath axes, on t, without unfolding t into a tree. To each Core XPath query of a certain basic type, we associate a word automaton; these automata run on the graph of dependency between the non-terminals of the straightline regular tre...

Several XML query languages have been proposed that use XPath expressions to locate data. But XPath expressions might miss some data because of irregularities in the data and schema of an XML data collection. In this paper we propose ApproXPath, which supports approximate path expressions. Approximate path expressions have the same syntax as XPath expressions, but allow content and structural e...

The satisfiability problem of queries is an important determinant in query optimization. The application of a satisfiability test can avoid the submission and the unnecessary evaluation of unsatisfiable queries, and thus save processing time and query costs. If an XPath query does not conform to constraints in a given schema, or constraints from the query itself are inconsistent with each other...

We present a query answering algorithm for a fragment of Forward XPath on Xml streams that we obtain by compilation to deterministic nested word automata. Our algorithm is earliest and in polynomial time. This proves the finite streamability of the fragment of Forward XPath with child steps, outermost-descendant steps, label tests, negation, and conjunction (aka filters), under the reasonable a...

In this paper, we investigate the complexity of deciding the satisfiability of XPath 2.0 expressions, i.e., whether there is an XML document for which their result is nonempty. Several fragments that allow certain types of expressions are classified as either in PTIME or NP-hard to see which type of expression make this a hard problem. Finally, we establish a link between XPath expressions and ...

We extend a recently proposed model checking-based algorithm for the evaluation of XPath queries with a cache strategy to store the results of the (most frequently) asked queries and to re-use them at occurrence. We experimentally show that, as soon as the cache is warm, the proposed optimization is quite effective. We complement our proposal with a broad experimental comparison of different st...

We present a novel solution to streaming XPath query evaluation, capable of supporting forward and reverse axes queries. We show a conversion of an XPath query to a Visibly Pushdown Automaton that preserves the semantics of the query. It was shown in [1] that such a construction results in an automation suitable for efficient streaming query evaluation. We also show that the constructed automat...

We propose XPathMark, an XPath benchmark on top of the XMark generated data. It consists of a set of queries which covers the main aspects of the language XPath 1.0. These queries have been designed for XML documents generated under XMark, a popular benchmark for XML data management. We suggest a methodology to evaluate the XPathMark on a given XML engine and, by way of example, we evaluate two...