We discuss incremental validation of XML documents with respect to DTDs and XML Schema definitions. We consider insertions and deletions of subtrees, as opposed to leaf nodes only, and we also consider the validation of ID and IDREF attributes. For arbitrary schemas, we give a worstcase time and linear space algorithm, and show that it often is far superior to revalidation from scratch. We present two classes of schemas, which capture most reallife DTDs, and show that they admit a logarithmic time incremental validation algorithm that, in many cases, requires only constant auxiliary space. We then discuss an implementation of these algorithms that is independent of, and can be customized for different storage mechanisms for XML. Finally, we present extensive experimental results showing that our approach is highly efficient and scalable.

Abstract. As XML schemas evolve over time or as applications are integrated, it is sometimes necessary to validate an XML document known to conform to one schema with respect to another schema. More generally, XML documents known to conform to a schema may be modified, and then, require validation with respect to another schema. Recently, solutions have been proposed for incremental validation of XML documents. These solutions assume that the initial schema to which a document conforms and the final schema with which it must be validated after modifications are the same. Moreover, they assume that the input document may be preprocessed, which in certain situations, may be computationally and memory intensive. In this paper, we describe how knowledge of conformance to an XML Schema (or DTD) may be used to determine conformance to another XML Schema (or DTD) efficiently. We examine both the situation where an XML document is modified before it is to be revalidated and the situation where it is unmodified. 1

We study the problem of storing XML documents using relational mappings. We propose a formalization of classes of mapping schemes based on the languages used for defining functions that assign relational databases to XML documents and vice-versa. We also discuss notions of information preservation for mapping schemes; we define lossless mapping schemes as those that preserve the structure and content of the documents, and validating mapping schemes as those in which valid documents can be mapped into legal databases, and all legal databases are (equivalent to) mappings of valid documents. We define one natural class of mapping schemes that captures all mappings in the literature, and show negative results for testing whether such mappings are lossless or validating. Finally, we propose a lossless and validating mapping scheme, and show that it performs well in the presence of updates. 1 1

Abstract. The W3C XML Schema recommendation defines the structure and data types for XML documents. XML Schema lacks explicit support for timevarying XML documents. Users have to resort to ad hoc, non-standard mechanisms to create schemas for time-varying XML documents. This paper presents a data model and architecture, called τXSchema, for creating a temporal schema from a non-temporal (snapshot) schema, a temporal annotation, and a physical annotation. The annotations specify which portion(s) of an XML document can vary over time, how the document can change, and where timestamps should be placed. The advantage of using annotations to denote the time-varying aspects is that logical and physical data independence for temporal schemas can be achieved while remaining fully compatible with both existing XML Schema documents and the XML Schema recommendation. 1

Current approaches for estimating the cardinality of XML queries are applicable to a static scenario wherein the underlying XML data does not change subsequent to the collection of statistics on the repository. However, in practice, many XML-based applications are dynamic and involve frequent updates to the data. In this paper, we investigate efficient strategies for incrementally maintaining statistical summaries as and when updates are applied to the data. Specifically, we propose algorithms that handle both the addition of new documents as well as random insertions in the existing document trees. We also show, through a detailed performance evaluation, that our incremental techniques are significantly faster than the naive recomputation approach; and that estimation accuracy can be maintained even with a fixed memory budget. 1.

Abstract: XML has emerged as the industry standard for representing and exchanging data and is already predominant in several applications today. Business, analytic and structered data will be exchanged as XML between applications and web services. XQuery is a language designed and developed for querying, filtering and generating XML structured data and is currently being standardized by the World Wide Web Consortium(W3C). XQuery seems to become the query language in context of (native) XML databases. Moreover in the context of document management XQuery seems suitable for querying large collections of documents with more irregular and deeply nested data structures. Despite these promising features XQuery or more precisely its FLWOR expression lacks of any update capability. In this paper we present important results concerning the development of XOBEDBPL (XML OBjEcts DataBase Programming Language). XOBEDBPL is the successor of the XOBE project. XOBE integrates XML and XPath into the Java programming language. In XOBEDBPL XML objects can become persistent. Moreover, a new feature in XOBEDBPL is the integration of xFLWOR(extended FLWOR) expressions for updating and querying XML objects. XML updates and queries in XOBEDBPL are statically typechecked. Finally we perform experiments with the XOBEDBPL prototype showing that the performance of low level API-based interfaces can be improved, as well as the performance of related approaches. 1

Abstract. We consider the problem of XML schema evolution preserving the validity of existing documents related to the original schema. The aim of such schema evolution is to fit new needs without revalidating all existing valid XML documents. We propose an approach to assist users to specify schema updates that have no impact on existing document validity. An XML schema is modeled as a set of regular expressions, each constraining the content model of XML elements. Given the user needs, we work on Glushkov graphs representing regular expressions E in the schema. By this way, we get straightforwardly the right places in E that may be changed while preserving validity.

XML is used for different purposes. We are interested in data-centric applications of XML where it is used to handle structured data in loosely coupled, distributed systems. In many such scenarios, it is important that the XML data complies to structural and integrity constraints, in particular to value-based constraints. The constraints should remain invariant under operations manipulating the data. In this paper, we present a technique to maintain the invariants. For a core procedural manipulation language, we show how to automatically derive the weakest precondition of procedures for the constraints. We present a formalization of a data-centric XML abstraction and an assertion language that enables weakest precondition generation. Our framework allows to automatically simplify and reduce the generated preconditions such that checking becomes independent of the size of the constraint definitions. This is achieved by isolating the aspects that are manipulated by the considered procedure from the aspects that remain unchanged. As the overall invariant can be assumed for the input data, only the isolated aspects have to be checked in prestates of procedures. 1.

The W3C XML Schema recommendation defines the structure and data types for XML documents. XML Schema lacks explicit support for time-varying XML documents. Users have to resort to ad hoc, non-standard mechanisms to create schemas for time-varying XML documents. This thesis presents a data model and architecture, called τXSchema, for creating a temporal schema from a non-temporal (snapshot) schema, a temporal annotation, and a physical annotation. The annotations specify which portion(s) of an XML document can vary over time, how the document can change, and where timestamps should be placed. The advantage of using annotations to denote the time-varying aspects is that logical and physical data independence for temporal schemas can be achieved while remaining fully compatible with both existing XML Schema documents and the XML Schema recommendation. This paper presents a system for constructing and validating temporal XML documents. An XML document evolves as it is updated over time or as it accumulates from a streaming data source. A temporal document records the entire history of a document rather than just its current state or snapshot. Capturing a document‘s evolution is vital to providing the ability to recover