Françoise Gire

Regular tree patterns: a uniform formalism for update queries and functional dependencies in XML

Given an XML functional dependency fd and a class of updates U, we say that fd is independent with respect to U if and only if any XML document satisfies fd after any update q of U, as soon as it did it before q. In this paper we study the following problem: is it possible to detect if an XML functional dependency fd is independent with respect to a class of updates U? We address this problem when the functional dependency and the class of updates are specified with a same formalism: the regular tree patterns. We first show that the use of regular tree patterns federates most of the known approaches for expressing XML functional dependencies while allowing to capture some of constraints not so far expressible. Then we show that in general the addressed problem is PSPACE-hard, but we exhibit a sufficient condition testable in polynomial time ensuring the independence of a functional dependency with respect to a class of updates.

Well Founded Semantics and Stable Semantics of Semi-Strict Programs

In this paper we exhibit a condition on the syntax of the logic programs with negation, the semi-strictness property, which assures the equivalence of the well founded semantics and the stable semantics: so, for semi-strict programs the well founded model is total if and only if the program has an unique stable model.

Requêtes arbres régulières pour l'analyse de dépendances entre vues et mises à jour de documents XML

In this paper we study the classical problem of the impact of an update on a view defined over semi-structured data. We adopt the following working hypotheses: (i) the source document is modeled by an unranked, labeled, ordered tree, (ii) a view V is a tree query whose evaluation on the source document provides a desired partial view of the document, (iii) a class of updates C. is also given by a tree query selecting the nodes to modify. We then study the following problem: given a view query V and a class of updates C., is it possible to detect if the view V is independent of each update q in C.? We show that the problem is in general PSPACE-hard. We propose a sufficient condition evaluable in polynomial time ensuring the independence of a view V with respect to a class of updates C.. We then consider the class of linear view queries for which the problem becomes polynomial. We also show that the tree query model chosen to express V and C., is incomparable with XPath but is able to capture positive queries of CoreXPath.

A More Expressive Deterministic Query Language with Efficient Symmetry-Based Choice Construct

In this paper, symmetry-based choice mechanisms are exploited to compute deterministic queries. We investigate a particular form of these choice mechanisms, called specified symmetry choice. This mechanism is efficient (i.e. computable in polynomial time) and can be added to Fixpoint Logic to give a language that is more powerful than the extension of Fixpoint with Counting.