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Inclusion between XML types is important but expensive, and is much more expensive when unordered types are considered. We prove here that inclusion for XML types with interleaving and counting can be decided in polynomial time in presence of two important restrictions: no element appears twice in the same content model, and Kleene star is only applied to(More)
A part of a query that will never contribute data to the query answer should be regarded as an error. This principle has been recently accepted into mainstream XML query languages, but was still waiting for a complete treatment. We provide here a precise definition for this class of errors, and define a type system that is sound and complete, in its search(More)
This paper describes XPeer, a zero-administration system for sharing and querying XML data. The system allows users to share XML data without significant human intervention, and to pose XQuery FLWR queries against them.The proposed system can be used in any application field, being a general purpose XML p2p DBMS, even though its main application is the(More)
This work presents the query language TQL, a query language for semistructured data, that can be used to query XML files. TQL substitutes the standard path-based pattern-matching mechanism with a logic-based mechanism , where the programmer specifies the properties of the pieces of data she is trying to extract. As a result, TQL queries are more(More)
If a subexpression in a query will never contribute data to the query answer, this should be regarded as an error. This principle has been recently accepted into mainstream XML query languages, but was still waiting for a complete treatment. We provide here a precise definition for this class of errors, and define a type system that is sound and complete,(More)
XML is nowadays considered the standard metalanguage for document markup and data representation. XML is widely employed in Web-related applications as well as in database applications, and there is also a growing interest for it by the literary community in order to develop tools for supporting document-oriented retrieval operations. The purpose of this(More)
The inclusion of Regular Expressions (REs) is the kernel of any subtype checking algorithm for XML schema languages. XML applications would benefit from the extension of REs with interleaving and counting, but this is not feasible in general, since inclusion is EXPSPACE-complete for such extended REs. In [9] we introduced a notion of "conflict-free REs",(More)
The extension of Regular Expressions (REs) with an interleaving (shuffle) operator has been proposed in many occasions, since it would be crucial to deal with unordered data. However, interleaving badly affects the complexity of basic operations, and, expecially, makes membership NP-hard [13], which is unacceptable for most uses of REs. REs form the basis(More)