Abstract. As XML applications become more complex, there is a growing interest in extending XQuery with side-effect operations, notably XML updates. However, the presence of side-effects is at odds with XQuery’s declarative semantics which leaves evaluation order unspecified. In this paper, we define “XQuery!”, an extension of XQuery 1.0 that supports first-class XML updates and user-level control over update application, preserving the benefits of XQuery’s declarative semantics when possible. Our extensions can be easily implemented within an existing XQuery processor and we show how to recover basic database optimizations for such a language. 1

Abstract. XQuery 1.0, the XML query language which is about to become a W3C Recommendation, lacks the ability to make persistent changes to instances of its data model. A number of proposals to extend XQuery with update facilities have been made lately, including a W3C Working Draft. In order to investigate some of the different constructs that are introduced in these proposals, we define an XQuerybased update language that combines them. By doing so, we show that it is possible to give a concise, complete and formal definition of such a language. We define subsets of this language to examine the relative expressive power of the different constructs, and we establish the relationships between these subsets in terms of queries and updates that can be expressed. Finally, we discuss the relationships between these subsets and existing XQuery-based update languages. 1

Abstract. A common approach to XML updates is to extend XQuery with update operations. This approach results in very expressive languages which are convenient for users but are difficult to reason about. Deciding whether two expressions can commute has numerous applications from view maintenance to rewriting-based optimizations. Unfortunately, commutativity is undecidable in most recent XML update languages. In this paper, we propose a conservative analysis for an expressive XML update language that can be used to determine whether two expressions commute. The approach relies on a form of path analysis that computes upper bounds for the nodes that are accessed or modified in a given update expression. Our main result is a commutativity theorem that can be used to identify commuting expressions. 1

Abstract. We address a problem of updating XML documents having their XML schema described by a Document Type Definition (DTD) without breaking their validity. We present a way how to express constructs available in DTD in a functional data model and propose algorithms for performing insert, update and delete operations. After that we embed the update capability into an existing query language for XML. This paper thus outlines the whole ”life cycle ” of the approach from the problem analysis to its implementation. 1

XML constraints are either schema constraints representing rules about document structure (e.g. a DTD, an XML Schema definition or a specification in Relax-NG), or integrity constraints, which are rules about the values contained in documents (e.g. primary keys, foreign keys, etc.). We address the problem of incrementally verifying these constraints when documents are modified by updates. The structure of an XML document is a tree, whose nodes are element (or attribute) names and whose leaves are associated to values contained in the document. Considered updates are insertion, deletion or replacement of any subtree in the XML tree. Schema constraints are represented by tree automata and tree grammars. Key and foreign key constraints are represented by attribute grammars, adding semantic rules to schema grammars, to carry key and foreign key values (to verify their properties). Our incremental validation tests both schema and integrity constraints while treating the sequence of updates, in only one pass over the document. Only nodes involved in updates trigger validation tests. An analysis of complexity shows that worst cases are determined by the shape of the XML tree being processed (asymptotic upper bounds are presented). Experimental results show that our algorithms behave efficiently in practice. Povzetek: Opisana je inkrementalna verifikacija podatkovnih baz XML. 1

Issues related to updating data in native XML database systems are studied extensively nowadays. In this work we consider a problem of updating typed XML documents having their schema described by a Document Type Definition (DTD) without breaking their validity and with ensured transaction consistency. We present a way how to express constructs available in DTD by using a functional framework and propose algorithms for performing insert, replace and delete operations. This solution is an intermediate step we need for our ongoing research – formal comparison of XQuery and XML-λ. 1

XML has been explored by both research and industry communities. More than 5500 papers were published on different aspects of XML. With so many publications, it is hard for someone to decide where to start. Hence, this paper presents some of the research topics on XML, namely: XML on relational databases, query processing, views, data matching, and schema evolution. It then summarizes some (some!) of the most relevant or traditional papers on those subjects. 1.