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this paper, we extend XML DTDs with several classes of integrity constraints and investigate the complexity of reasoning about these constraints. The constraints range over keys, foreign keys, inverse constraints as well as ID constraints for capturing the semantics of object identities. They improve semantic specifications and provide a better reference mechanism for native XML applications. They are also useful in information exchange and data integration for preserving the semantics of data originating in relational and object-oriented databases. We establish complexity and axiomatization results for the (finite) implication problems associated with these constraints. In addition, we study implication of more general constraints, such as functional, inclusion and inverse constraints defined in terms of navigation paths

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This paper investigates that interaction. In particular it studies constraint implication problems, which are important both in understanding the semantics of type/constraint systems and in query optimization. It shows that path constraints interact with types in a highly intricate way. For that purpose a number of results on path constraint implication are established in the presence and absence of type systems. These results demonstrate that adding a type system may in some cases simplify reasoning about path constraints and in other cases make it harder. For example, it is shown that there is a path constraint implication problem that is decidable in PTIME in the untyped context, but that becomes undecidable when a type system is added. On the other hand, there is an implication problem that is undecidable in the untyped context, but becomes not only decidable in cubic time but also finitely axiomatizable when a type system is imposed

this paper is to rectify this problem, by integrating aspects of the research of [BW94] into DLs. We point out that the success of this integration is not a priori expected because their data model does not involve concept definitions, which would correspond to views in OODB, yet the main concern of DLs is exactly with reasoning about such view definitions. 1.1 Description Logics DLs are used to describe situations using various kinds of individuals (objects), related by relationships, which we call here attributes, and grouped into sets (classes/concepts)

. We establish the equivalence of: (1) the logical implication problem for a description logic dialect called DLClass that includes a concept constructor for expressing uniqueness constraints, (2) the logical implication problem for path functional dependencies (PFDs), and (3) the problem of answering queries in deductive databases with limited use of successor functions. As a consequence, we settle an open problem concerning lower bounds for the PFD logical implication problem and show that a regularity condition for DLClass that ensures low order polynomial time decidability for its logical implication problem is tight.

Virtually all semantic or object-oriented data models assume objects have an identity separate from any of their parts, and allow users to define complex object types in which part values may be any other objects. In [20], a more general form of functional dependency is proposed for such models in which component attributes may correspond to descriptions of property paths, called path functional dependencies (PFDs). The main contribution of the reference is a sound and complete axiomatization for PFDs when databases may be infinite. However, a number of issues were left open which are resolved in this paper. We first prove that the same axiomatization remains complete if PFDs are permitted empty left-hand sides, but that this is not true if logical consequence is defined with respect to finite databases. We then prove that the implication problem for arbitrary PFDs is decidable. The proof suggests a means of characterizing an important function closure which is then used to derive an effective procedure for constructing a deterministic finite state automation representing the closure. The procedure is further refined to efficient polynomial time algorithms for the implication problem for cases in which antecedent PFDs are a form of complex key constraint. Index Terms: constraints, functional dependencies, object-oriented data models, complex objects, implication problems

Integrity constraints play a fundamental role in database design. We review initial work on the expression of integrity constraints for semistructured data and XML.

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. Queries commonly perform much better if they manage to avoid duplicate elimination operations in their execution plans. In this paper, we report on a technique that provides a necessary and sucient condition for removing such operators from object relational conjunctive queries under the standard duplicate semantics. The condition is fully captured as a membership problem in a dialect of description logic called CFD, which is capable of expressing a number of common constraints implicit in object relational database schemas. We also present a PTIME algorithm for arbitrary membership problems in CFD. 1 Introduction The paper presents a combination of two techniques to provide a very powerful tool for reasoning about duplicate semantics of conjunctive object relational queries, in particular about elimination operations and situations in which these operations can be completely removed. The query language studied in the paper contains many other practical query languages, in ...