38767
Inferring structure in semistructured data
When dealing with semistructured data such as that available on the Web, it becomes important to infer the inherent structure, both for the user (e.g., to facilitate querying) and for the system (e.g., to optimize access). In this paper, we consider the problem of identifying some underlying structure in large collections of semistructured data. Since we expect the data to be fairly irregular, this structure consists of an approximate classification of objects into a hierarchical collection of types. We propose a notion of a type hierarchy for such data, and outline a method for deriving the type hierarchy, and rules for assigning types to data elements.
53236199
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 to materialize the intensional data (i.e. to invoke the embedded calls) or not, before the document is sent. This choice may be influenced by various parameters, such as performance and security considerations. This paper addresses the problem of guiding this materialization process.We argue that, just like for regular XML data, schemas (ala DTD and XML Schema) may 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 [3, 1].
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.
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.
5860221
Diagnosis of asynchronous discrete event systems: datalog to the rescue!
We consider query optimization techniques for data intensive P2P applications. We show how to adapt an old technique from deductive databases, namely Query-Sub-Query (QSQ), to a setting where autonomous and distributed peers share large volumes of interelated data.We illustrate the technique with an important telecommunication problem, the diagnosis of distributed telecom systems. We show that (i) the problem can be modeled using Datalog programs, and (ii) it can benefit from the large battery of optimization techniques developed for Datalog. In particular, we show that a simple generic use of the extension of QSQ achieves an optimization as good as that previously provided by dedicated diagnosis algorithms. Furthermore, we show that it allows solving efficiently a much larger class of system analysis problems.
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.
43817205
Constructing and Querying Peer-to-Peer Warehouses of XML Resources
We present KadoP, a distributed infrastructure for warehousing XML resources in a peer-to-peer framework. KadoP allows users to build a shared, distributed repository of resources such as XML documents, semantic information about such documents, Web services, and collections of such items. KadoP2P builds on distributed hash tables as a peer communication layer, and ActiveXML as a model for constructing and querying the resources in the peer network. We describe KadoP's data model, query language, and query processing paradigm.
14194921
Active XML, Security and Access Control
XML and Web services are revolutioning the automatic management of distributed information, somewhat in the same way that HTML, Web browsers and search engines modified human access to world wide information. We argue in this paper that the combination of XML and Web services allows for a novel distributed data management paradigm, where the exchanged information mixes materialized and intensional, active, information. We illustrate the flexibility of this approach by presenting Active XML, a language that is based on embedding Web service calls in XML data. We focus on two particular issues, namely security and access control.
11287865
The Data Ring: Community Content Sharing
Information ubiquity has created a large crowd of users (most notably scientists), who could employ DBMS technol- ogy to process and share their data more e!ec tively. Still, this user base prefers to keep its data in files that can be easily managed by applications such as spreadsheets, rather than deal with the complexity and rigidity of modern database systems. In this paper, we propose a vision for enabling non-experts, such as scientists, to build content sharing communities in a true database fashion: declaratively. The proposed infras- tructure, called the data ring, enables users to manage and share their data with minimal e! ort; the user points to the data that should be shared, and the data ring becomes re- sponsible for automatically indexing the data (to make it accessible), replicating it (for availability), and reorganiz- ing its physical storage (for better query performance). We outline the salient features of our proposal, and outline re- search challenges that must be addressed in order to realize this vision.
9941016
A First Experience in Archiving the French Web
The web is a more and more valuable source of information and organizations are involved in archiving (portions of) it for various purposes, e.g., the Internet Archive www.archive.org. A new mission of the French National Library (BnF) is the "depot legal" (legal deposit) of the French web. We describe here some preliminary work on the topic conducted by BnF and INRIA. In particular, we consider the acquisition of the web archive. Issues are the definition of the perimeter of the French web and the choice of pages to read once or more times (to take changes into account). When several copies of the same page are kept, this leads to versioning issues that we briefly consider. Finally, we mention some first experiments.