The development of new Web services through the composition of existing ones has gained a considerable momentum as a means to realise business-to-business collaborations. Unfortunately, given that services are often developed in an ad hoc fashion using manifold technologies and standards, connecting and coordinating them in order to build composite services is a delicate and time-consuming task. In this paper, we describe the design and implementation of a system in which services are composed using a model-driven approach, and the resulting composite services are orchestrated following a peer-to-peer paradigm. The system provides tools for specifying composite services through statecharts, data conversion rules, and multi-attribute provider selection policies. These specifications are interpreted by software components that interact in a peer-to-peer way to coordinate the execution of the composite service. We report results of an experimental evaluation showing the relative advantages of this peer-to-peer approach with respect to a centralised one.

The two observations that 1) many XML documents are stored in a database or generated from data stored in a database and 2) processing these documents with XSL stylesheet processors is an important, often recurring task justify a closer look at the current situation. Typically, the XML document is retrieved or constructed from the database, exported, parsed, and then processed by a special XSL processor. This cumbersome process clearly sets the goal to incorporate XSL stylesheet processing into the database engine.

XML has reached a widespread diffusion as a language for representing nearly any kind of data source, from relational databases to digital movies. Due to the growing interest toward XML, many tools for storing, processing, and querying XML data have appeared in the last two years. Three main problems affect XML query processing: path expression evaluation, nested query resolution, and preservation of document order. These issues, which are related to the hierarchical structure of XML and to the features of current XML query languages, require compile-time as well as run-time solutions. This paper describes a query algebra for XML data. The main purpose of this algebra, which forms the basis for the Xtasy database management system, is to combine good optimization properties with a good expressive power that allows it to model significant fragments of current XML query languages; in particular, explicit support is given to efficient path expression evaluation, nested query resolution, and order preservation.

The Semantic Web would enable new ways of doing business on the Web that require development of advanced business document integration technologies performing intelligent document transformation. The

We have implemented and released the XSQ system for evaluating XPath queries on streaming XML data. XSQ supports XPath features such as multiple predicates, closures, and aggregation, which pose interesting challenges for streaming evaluation. Our implementation is based on using a hierarchical arrangement of augmented finite state automata. A design goal of XSQ is buffering data for the least amount of time possible. We present a detailed experimental study that characterizes the performance of XSQ and related systems, and that illustrates the performance implications of XPath features such as closures.

Abstract. The Business Process Execution Language (BPEL) has become the dominant means for expressing traditional business processes as workflows. The widespread deployment of mobile devices like PDAs and mobile phones has created a vast computational and communication resource for these workflows to exploit. However, BPEL so far has been deployed only on relatively heavyweight server platforms such as Apache Tomcat, leaving the potential created by these lower-end devices untapped. This paper presents Sliver, a BPEL workflow process execution engine that supports a wide variety of devices ranging from mobile phones to desktop PCs. We discuss the design decisions that allow Sliver to operate within the limited resources of a mobile phone or PDA. We also evaluate the performance of a prototype implementation of Sliver. 1

Managing traceability data is an important aspect of the software development process. In this paper we investigate to what extent latent semantic indexing (LSI), an information retrieval technique, can help recovering the information needed for automatically reconstructing traceability during the development process. We experimented with two different link selection strategies and applied LSI in multiple case studies varying in size and context. We discuss the results of a small lab study, a larger case study and a large industrial case study. 1.

While the information published in the form of XML-compliant documents keeps fast mounting up, efficient and effective query processing and optimization for XML have now become more important than ever. This article reports our recent advances in XML structureddocument query optimization. In this article, we elaborate on a novel approach and the techniques developed for XML query optimization. Our approach performs heuristic-based algebraic transformations on XPath queries, represented as PAT algebraic expressions, to achieve query optimization. This article first presents a comprehensive set of general equivalences with regard to XML documents and XML queries. Based on these equivalences, we developed a large set of deterministic algebraic transformation rules for XML query optimization. Our approach is unique, in that it performs exclusively deterministic transformations on queries for fast optimization. The deterministic nature of the proposed approach straightforwardly renders high optimization efficiency and simplicity in implementation. Our approach is a logical-level one, which is independent of any particular storage model. Therefore, the optimizers developed based on our approach can be easily adapted to a broad range of XML data/information servers to achieve fast query optimization. Experimental study confirms the validity and effectiveness of the proposed approach.

This paper introduces an algebraic framework for expressing and evaluating queries over XML data. It presents the underlying assumptions of the framework, describes the input and output of the algebraic operators, and defines these operators and their semantics. It evaluates the framework with regard to other proposed XML query algebras. Examples show that this framework is flexible enough to capture queries expressed in Quilt, one of the dominant XML query languages. We have used this algebra in the context of an Internet query engine, in which it is used to formulate logical plans for XML-QL queries. We define equivalence rules that provide opportunities for optimization, and give example cases that point out the usefulness of these rules. 1

Abstract — Streams are preferable over data stored in memory in contexts where data is too large or volatile, or a standard approach to data processing based on storing is too time or space consuming. Emerging applications such as publishsubscribe systems, data monitoring in sensor networks, financial and traffic monitoring, and routing of MPEG-7 call for querying streams. In many such applications, XML streams are arguably more appropriate than flat streams, for they convey (possibly unbounded) unranked ordered trees with labeled nodes. However, the flexibility enabled by XML streams in data modeling makes query evaluation different from traditional settings and challenging. This article describes SPEX, a streamed and progressive evaluation of XPath. SPEX compiles queries into networks of simple and independent transducers and processes XML streams with polynomial combined complexity. This makes SPEX especially suitable for implementation on devices with low-memory and simple logic as used, e.g., in mobile computing.