9888780
DBGlobe: a service-oriented P2P system for global computing
The challenge of peer-to-peer computing goes beyond simple file sharing. In the DBGlobe project, we view the multitude of peers carrying data and services as a superdatabase. Our goal is to develop a data management system for modeling, indexing and querying data hosted by such massively distributed, autonomous and possibly mobile peers. We employ a service-oriented approach, in that data are encapsulated in services. Direct querying of data is also supported by an XML-based query language. In this paper, we present our research results along the following topics: (a) infrastructure support, including mobile peers and the creation of context-dependent communities, (b) metadata management for services and peers, including location-dependent data, (c) filters for efficiently routing path queries on hierarchical data, and (d) querying using the AXML language that incorporates service calls inside XML documents.
46518675
Managing an XML Warehouse in a P2P Context
The paper is about warehousing XML content in a P2P environment. The role of an XML warehouse is to offer a centralized entry point to access a variety of information in an enterprise and provide functionalities to acquire, enrich, monitor and maintain this information. We consider a number of reasons to use a P2P approach to such warehouses, e.g., reducing the cost or sharing the management of information. We mention research issues that are raised.
1233326
Turning the Network into a Database with Active XML
Because of information ubiquity, one observes an important trend towards transferring information management tasks from database systems to networks. We introduce the notion of data ring that can be seen as a network version of a database or a content warehouse. A main goal is to achieve better performance for content management without requiring the acquisition of explicit control over information resources. In this paper, we discuss the main traits of data rings and argue that Active XML provides an appropriate basis for such systems.
39011254
Correspondence and Translation for Heterogeneous Data
We presented a specification of the integration of heterogeneous data based on correspondence rules. We showed how a unique specification can served many purposes (including two-way translation) assuming some reasonable restrictions. We claim that the framework and restrictions are acceptable in practice, and in particular one can show that all the document-OODB correspondences/translations of [2, 3] are covered. We are currently working on further substantiating this by more experimentation.
1444961
Compact Labeling Scheme for Ancestor Queries
We consider the following problem. Given a rooted tree $T$, label the nodes of $T$ in the most compact way such that, given the labels of two nodes $u$ and $v$, one can determine in constant time, by looking only at the labels, whether $u$ is ancestor of $v$. The best known labeling scheme is rather straightforward and uses labels of length at most $2\log_2 n$ bits each, where $n$ is the number of nodes in the tree. Our main result in this paper is a labeling scheme with maximum label length $\log_2 n + \Oh(\sqrt{\log n})$. Our motivation for studying this problem is enhancing the performance of web search engines. In the context of this application each indexed document is a tree, and the labels of all trees are maintained in main memory. Therefore even small improvements in the maximum label length are important.
5096355
Dynamic XML documents with distribution and replication
The advent of XML as a universal exchange format, and of Web services as a basis for distributed computing, has fostered the apparition of a new class of documents: dynamic XML documents. These are XML documents where some data is given explicitly while other parts are given only intensionally by means of embedded calls to web services that can be called to generate the required information. By the sole presence of Web services, dynamic documents already include inherently some form of distributed computation. A higher level of distribution that also allows (fragments of) dynamic documents to be distributed and/or replicated over several sites is highly desirable in today's Web architecture, and in fact is also relevant for regular (non dynamic) documents.The goal of this paper is to study new issues raised by the distribution and replication of dynamic XML data. Our study has originated in the context of the Active XML system [1, 3, 22] but the results are applicable to many other systems supporting dynamic XML data. Starting from a data model and a query language, we describe a complete framework for distributed and replicated dynamic XML documents. We provide a comprehensive cost model for query evaluation and show how it applies to user queries and service calls. Finally, we describe an algorithm that, for a given peer, chooses data and services that the peer should replicate to improve the efficiency of maintaining and querying its dynamic data.
726310
Exchanging intensional XML data
XML is becoming the universal format for data exchange between applications. Recently, the emergence of Web services as standard means of publishing and accessing data on the Web introduced a new class of XML documents, which we call intensional documents. These are XML documents where some of the data is given explicitly while other parts are defined only intensionally by means of embedded calls to Web services.When such documents are exchanged between applications, one has the choice of whether or not to materialize the intensional data (i.e., to invoke the embedded calls) before the document is sent. This choice may be influenced by various parameters, such as performance and security considerations. This article addresses the problem of guiding this materialization process.We argue that---like for regular XML data---schemas (à la DTD and XML Schema) can be used to control the exchange of intensional data and, in particular, to determine which data should be materialized before sending a document, and which should not. We formalize the problem and provide algorithms to solve it. We also present an implementation that complies with real-life standards for XML data, schemas, and Web services, and is used in the Active XML system. We illustrate the usefulness of this approach through a real-life application for peer-to-peer news exchange.
1109183
XML Data Integration with Identification
Data integration is the problem of combining data residing at different sources, and providing the user with a virtual view, called global schema, which is independent from the model and the physical origin of the sources. Whereas many data integration systems and theoretical works have been proposed for relational data, not much investigation has been focused yet on XML data integration. Our goal is therefore to address some of its related issues. In particular, we highlight two major issues that emerge in the XML context: (i) the global schema may be characterized by a set of constraints, expressed by means of a DTD and XML integrity constraints, (ii) the concept of node identity requires to introduce semantic criteria to identify nodes coming from different sources. We propose a formal framework for XML data integration systems based on an expressive XML global schema, a set of XML data sources and a set of mappings specified by means of a simple tree language. Then, we define an identification function that aims at globally identifying nodes coming from different sources. Finally, we propose algorithms to answer queries under different assumptions for the mappings.
965218
Positive active XML
The increasing popularity of XML and Web services have given rise to a new generation of documents, called Active XML documents (AXML), where some of the data is given explicitly while other parts are given intensionally, by means of embedded calls to Web services. Web services in this context can exchange intensional information, using AXML documents as parameters and results.The goal of this paper is to provide a formal foundation for this new generation of AXML documents and services, and to study fundamental issues they raise. We focus on Web services that are (1) monotone and (2) defined declaratively as conjunctive queries over AXML documents. We study the semantics of documents and queries, the confluence of computations, termination and lazy query evaluation.
1932947
Representing and querying XML with incomplete information
We study the representation and querying of XML with incomplete information. We consider a simple model for XML data and their DTDs, a very simple query language, and a representation system for incomplete information in the spirit of the representations systems developed by Imielinski and Lipski [1984] for relational databases. In the scenario we consider, the incomplete information about an XML document is continuously enriched by successive queries to the document. We show that our representation system can represent partial information about the source document acquired by successive queries, and that it can be used to intelligently answer new queries. We also consider the impact on complexity of enriching our representation system or query language with additional features. The results suggest that our approach achieves a practically appealing balance between expressiveness and tractability.
2062723
Active XML: A Data-Centric Perspective on Web Services
We propose in this chapter a peer-to-peer architecture that allows for the integration of distributed data and Web services. It relies on a language, Active XML, where documents embed calls to Web services that are used to enrich them, and new Web services may be defined by XQuery queries on such active documents. Embedding calls to functions or even to Web services inside data is not a new idea. Our contribution, however, is to turn them into a powerful tool for data and services integration. In particular, the language includes linguistic features to control the timing of service call activations. Various scenarios are captured, such as mediation, data warehousing and distributed computation. A first prototype is also described.