XML is becoming the most relevant new standard for data representation and exchange on the WWW. Novel languages for extracting and restructuring the XML contenthave been proposed, some in the tradition of database query languages #i.e. SQL, OQL#, others more closely inspired by XML. No standard for XML query language has yet been decided, but the discussion is ongoing within the World Wide Web Consortium and within many academic institutions and Internet-related major companies. We present a comparison of #ve, representative query languages for XML, highlighting their common features and di#erences. 1 Introduction to the #ve languages 1.1 LOREL LOREL was originally designed for querying semistructured data and has now been extended to XML data; it was conceived and implemented at Stanford University #S. Abiteboul, D. Quass, J. McHugh, J. Widom, J. Wiener# and its prototype is at http:##www-db.stanford.edu#lore. It is a user-friendly language in the SQLnOQL style, it includes a...

Abstract. Based on the recursion mechanism of the XML transformation language XSL, the document transformation language DTL is defined. First the instantiation DTL reg is considered that uses regular expressions as pattern language. This instantiation closely resembles the navigation mechanism of XSL. For DTL reg the complexity of relevant decision problems such as termination of programs, usefulness of rules and equivalence of selection patterns, is addressed. Next, a much more powerful abstraction of XSL is considered that uses monadic second-order logic formulas as pattern language (DTL mso). If DTL mso is restricted to top-down transformations (DTL mso d), then a computational model can be defined which is a natural generalization to unranked trees of topdown tree transducers with look-ahead. The look-ahead can be realized by a straightforward bottom-up pre-processing pass through the document. The size of the output of an XSL program is at most exponential in the size of the input. By restricting copying in XSL a decidable fragment of DTL mso d programs is obtained which induces transformations of linear size increase (safe DTL mso d). It is shown that the emptiness and finiteness problems are decidable for ranges of DTL mso d programs and that the ranges are closed under intersection with generalized Document Type Definitions (DTDs). 1

This paper presents a novel editor supporting interactive refinement in the development of structured documents. The user performs a sequence of editing operations on the document view, and the editor automatically derives an efficient and reliable document source and a transformation that produces the document view. The editor is unique in its programmability, in the sense that transformation can be obtained through editing operations. The main tricks behind are the utilization of the view-updating technique developed in the database community, and a new bidirectional transformation language that cannot only describe the relationship between the document source and its view, but also data dependency in the view.

Over the last few years, efficient access to heterogeneous data sources has become tremendously important. One common technique for increasing efficiency is to maintain locally stored views in data warehouses, which must be kept current with respect to the changes in the underlying data sources. While this problem has been extensively studied in the context of select-project-join (SPJ) views and relational warehouses, many of the data sources accessible today over the Web are highly irregular. Views over this irregular data often perform complex restructuring and regrouping far beyond traditional SPJ views. This paper describes WHAX (Warehouse Architecture for XML), an architecture for defining and maintaining views over hierarchical semistructured data and relational data sources with key constraints. The WHAX model is a variant of the deterministic model of [8], but is more reminiscent of XML. The view definition language is a variation of XML-QL that has been adapted to the ...

Abstract. A generic function is defined by induction on the structure of types. The structure of a data type can be defined in several ways. For example, in PolyP a pattern functor gives the structure of a data type viewed as a fixed point, and in Generic Haskell a structural representation type gives an isomorphic type view of a data type in terms of sums of products. Depending on this generic view on the structure of data types, some generic functions are easier, more difficult, or even impossible to define. Furthermore, the efficiency of some generic functions can be improved by choosing a different view. This paper introduces generic views on data types and shows why they are useful. Furthermore, it shows how generic views have been added to Generic Haskell, an extension of the functional programming language Haskell that supports the construction of generic functions. The separation between inductive definitions on type structure and generic views allows us to combine many approaches to generic programming in a single framework. 1

We address the problem of tight XML schemas and propose regular tree automata to model XML data. We show that the tree automata model is more powerful that the XML DTDs and is closed under main algebraic operations. We introduce the XML query algebra based the tree automata model, and discuss the query optimization and query pruning techniques. Finally, we show the conversion of tree automata schema into XML DTDs.

In many occasions would one encounter the task of maintaining the consistency of two pieces of structured data that are related by some transform --- synchronising bookmarks in di#erent web browsers, the source and the view in an editor, or views in databases, to name a few. This paper proposes a formal model of such tasks, basing on a programming language allowing injective functions only. The programmer designs the transformation as if she is writing a functional program, while the synchronisation behaviour is automatically derived by algebraic reasoning. The main advantage is being able to deal with duplication and structural changes. The result will be integrated to our structure XML editor in the Programmable Structured Document project.

Existing systems for XML views only support selection operation applied in the views and cannot validate views. In this paper, we propose a systematic approach to design valid XML views. First, we transform the semistructured XML source documents into a semantically rich Object-RelationshipAttribute model designed for SemiStructured data (ORA-SS). Second, we enrich the ORA-SS diagram with semantics such as participation constraints of object classes and distinguishing between attributes of object classes and relationship types, which cannot be expressed in the XML document. Third, we use the additional semantics to develop a set of rules to guide the design of valid XML views. We identify four transformation operations for creating XML views, namely, selection, projection, join and swap operation. Finally, we develop a comprehensive algorithm that checks for the validity of XML views constructed by applying the four operations.

XML is just becoming a standard for document processing and interchange on the Internet. In this context, XML's DTD structuring mechanism is especially important. This paper addresses, among others, the problem of integration of several DTDs by introducing a grammar based model for XML based on so called xtrees and xschemes. Although it can be shown that we can always find a DTD describing the intersection of the languages defined by two arbitrarily given DTDs, the same is not true for the union. This result shows that pure DTDs are not sufficient for schema integration. The paper presents a solution to this problem by introducing and investigating a generalized model based on so called s-xschemes. Using these s-xschemes we can obtain additional information about XML documents belonging to certain classes, thus enabling computation and transformation of information more specifically.

Recent trends in information management involve the periodic transcription of data onto secondary devices in a networked environment, and the proper scheduling of these transcriptions is critical for efficient data management. To assist in the scheduling process, we are interested in modeling data obsolescence, that is, the reduction of consistency over time between a relation and its replica. The modeling is based on techniques from the field of stochastic processes, and provides several stochastic models for content evolution in the base relations of a database, taking referential integrity constraints into account. These models are general enough to accommodate most of the common scenarios in databases, including batch insertions and life spans both with and without memory. As an initial "proof of concept" of the applicability of our approach, we validate the insertion portion of our model framework via experiments with real data feeds. We also discuss a set of transcription protocols which make use of the proposed stochastic model.