U.C. San Diego

Abstract. This paper deals with some modeling aspects that have to be addressed in the context of the integration of heterogeneous and autonomous XML resources. We propose an integration system, but the emphasis of this paper is neither on its algorithmic aspects nor on its technical details. Instead, we focus on the significance of offering appropriate high-level primitives and mechanisms for representing the semantics of XML data. We posit that support for such primitives and mechanisms is a pre-requisite for realizing the goals of the semantic Web. 1

XML specifications often consist of a type definition (typically, a DTD) and a set of integrity constraints. It has been shown previously that such specifications can be inconsistent, and thus it is often desirable to check consistency at compile-time. It is known that for general keys and foreign keys, and DTDs, the consistency problem is undecidable; however, it becomes NP-complete when all keys are one-attribute (unary), and tractable, if no foreign keys are used.

Normalization as a way of producing good database designs is a well-understood topic.

In this article, we address the problem of how to extend the definition of functional dependencies (FDs) in incomplete relations to XML documents (called XFDs) using the well-known strong satisfaction approach.We propose a syntactic definition of strong XFD satisfaction in an XML document and then justify it by showing that, similar to the case in relational databases, for the case of simple paths, keys in XML are a special case of XFDs. We also propose a normal form for XML documents based on our definition of XFDs and provide a formal justification for it by proving that it is a necessary and sufficient condition for the elimination of redundancy in an XML document.

XML has become an important medium for data exchange, and is also used as an interface to -- i.e. a view of -- a relational database. While previous work has considered XML views for the purpose of querying relational databases (e.g. Silkroute), in this paper we consider the problem of updating a relational database through an XML view. Using the nested relational algebra as the formalism for an XML view of a relational database, we study the problem of when such views are updatable. Our results rely on the observation that in many XML views of relational databases, the nest operator occurs last and the unnest operator does not occur at all. Since in this case the nest operator is invertible, we can consider this important class of XML views as if they were flat relational views.

Abstract. We define a boolean complete description logic dialect called DLFDreg that can be used to reason about structural equality in semistructured ordered data in the presence of document type definitions. This application depends on the novel ability of DLFDreg to express functional dependencies over sets of possibly infinite feature paths defined by regular languages. We also present a decision procedure for the associated logical implication problem. The procedure underlies a mapping of such problems to satisfiability problems of Datalog ∨,¬ nS and in turn to the Ackermann case of the decision problem. 1

Current techniques for storing XML using relational technology consider the structure of an XML document but ignore its semantics as expressed by keys or functional dependencies. However, when the semantics of a document are considered redundancy may be reduced, node identifiers removed where value-based keys are available, and semantic constraints validated using relational primary key technology.

This paper reviews the recent developments in specification languages, static and run-time analyses as well as applications of integrity constraints for XML. 1

... In this chapter, we shall see that the suspicion is easy dispelled. We look at techniques now used in practice for dealing with XML trees, and we note how they depart from old-fashioned uses. Since trees are objects that are very complicated to manipulate directly through pointer updates, declarative techniques are becoming increasingly important, especially when it comes to exploring, mining, and constructing tree-shaped data. In particular, we will contrast conventional concepts of database theory such as relational calculus with that of more procedural notations for trees. We explore why the essential problem of locating data in trees is intimately linked with tree automata and decidable logics, somewhat in parallel to the link between query algebras and first-order logic in relational database theory. So, we shall see why logic and automata create interesting new research opportunities.