Balder ten Cate

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XPath is a prominent W3C standard for navigating XML documents that has stimulated a lot of research into query answering and static analysis. In particular, query containment has been studied extensively for fragments of the 1.0 version of this standard, whereas little is known about query containment in (fragments of) the richer language XPath 2.0. In(More)
We extend Core XPath, the navigational fragment of XPath 1.0, with transitive closure and path equalities. The resulting language, Regular XPATH<sup>&#8776;</sup>, is expressively complete for FO* (first-order logic extended with a transitive closure operator that can be applied to formulas with exactly two free variables). As a corollary, we obtain that(More)
A schema mapping is a specification of the relationship between a source schema and a target schema. Schema mappings are fundamental building blocks in data integration and data exchange and, as such, obtaining the right schema mapping constitutes a major step towards the integration or exchange of data. Up to now, schema mappings have typically been(More)
Schema mappings are declarative specifications that describe the relationship between two database schemas. In recent years, there has been an extensive study of schema mappings and of their applications to several different data inter-operability tasks, including applications to data exchange and data integration. Schema mappings are expressed in some(More)
The first aim of this paper is to present the logical core of XPath 2.0: a logically clean, decidable fragment, which includes most navigational features of XPath 2.0 (complex counting conditions and data joins are not supported, as they lead to undecidability). The second aim is to provide a list of equations completely axiomatizing query equivalence in(More)
Hybrid languages are modal languages that have special symbols for naming individual states in models. Their history can be traced back to work of Arthur Prior in the fifties. The subject has recently regained interest, resulting in many new results and techniques. This chapter contains a modern overview of the field. We sketch its history, and survey the(More)
The LogicBlox system aims to reduce the complexity of software development for modern applications which enhance and automate decision-making and enable their users to evolve their capabilities via a ``self-service'' model. Our perspective in this area is informed by over twenty years of experience building dozens of mission-critical enterprise applications(More)
We consider the navigational core of XPath, extended with two operators: the Kleene star for taking the transitive closure of path expressions, and a subtree relativisation operator, allowing one to restrict attention to a specific subtree while evaluating a subexpression. We show that the expressive power of this XPath dialect equals that of FO(MTC), first(More)