14211244
Querying and Updating Probabilistic Information in XML
We present in this paper a new model for representing probabilistic information in a semi-structured (XML) database, based on the use of probabilistic event variables. This work is motivated by the need of keeping track of both confidence and lineage of the information stored in a semi-structured warehouse. For instance, the modules of a (Hidden Web) content warehouse may derive information concerning the semantics of discovered Web services that is by nature not certain. Our model, namely the fuzzy tree model, supports both querying (tree pattern queries with join) and updating (transactions containing an arbitrary set of insertions and deletions) over probabilistic tree data. We highlight its expressive power and discuss implementation issues.
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.
847694
Reasoning about XML update constraints
We introduce in this paper a class of constraints for describing howan XML document can evolve, namely XML update constraints. For these constraints, we study the implication problem, giving algorithms and complexity results for constraints of varying expressive power. Besides classical constraint implication, we also consider an instance-based approach. More precisely, we study implication with respect to a current tree instance, resulting from a series of unknown updates. The main motivation of our work is reasoning about data integrity under update restrictions in contexts where owners may lose control over their data, such as in publishing or exchange.
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.
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.
140229514
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 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. The research presented here was motivated by the Xyleme project at INRIA, whose objective it to develop a data warehouse for Web XML documents.
2750139
Regular rewriting of active XML and unambiguity
We consider here the exchange of Active XML (AXML) data, i.e., XML documents where some of the data is given explicitly while other parts are given only intensionally as calls to Web services. Peers exchanging AXML data agree on a data exchange schema that specifies in particular which parts of the data are allowed to be intensional. Before sending a document, a peer may need to rewrite it to match the agreed data exchange schema, by calling some of the services and materializing their data. Previous works showed that the rewriting problem is undecidable in the general case and of high complexity in some restricted cases. We argue here that this difficulty is somewhat artificial. Indeed, we study what we believe to be a more adequate, from a practical view point, rewriting problem that is (1) in the spirit of standard 1-unambiguity constraints imposed on XML schema and (2) can be solved by a single pass over the document with a computational device not stronger than a finite state automation. Following previous works, we focus on the core of the problem, i.e., on the problem on words. The results may be extended to (A)XML trees in a straightforward manner.
31547105
Secure Exchange of Modifiable Data and Queries
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.
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.