Abstract: This paper presents a generic model called TGV for efficient evaluation
of XQuery in a heterogeneous distributed system.
XQuery is a rich and so a complex language that allows users to express
a large scale of queries over XML documents. This expressiveness makes
difficulties to obtain an exclusive internal representation within a
system. To this purpose, models based on Tree Patterns have been
proposed: TPQ [1], generalized by the GTP
[2]. However, they do not capture well all the expressivity
of XQuery, cannot handle mediation problems, and do not support
extensible optimisation and sources information..
We present a tree pattern-based model called TGV that
* integrates the whole functionalities of XQuery
* uses an intuitive representation that provides a global
visualization of the request in a mediation context
* provides a framework for extensible optimization using a rules
definition model
* take into account all knowledges useful for the query evaluation
(cost model, accuracy, etc.)
This work has been implemented in the XLive system [#!dangngoc2005!#]
based on a full-XML architecture.
Abstract: XML has emerged as the leading language for representing and exchanging data
not only on the Web, but also in general in the enterprise. XQuery is emerging as the
standard query language for XML. Thus, tools are required to mediate between XML
queries and heterogeneous data sources to integrate data in XML. This paper presents the
XMedia mediator, a unique tool for integrating and querying disparate heterogeneous
information as unified XML views. It describes the mediator architecture and focuses on the
unique distributed query processing technology implemented in this component. Query
evaluation is based on an original XML algebra simply extending classical operators to
process tuples of tree elements. Further, we present a set of performance evaluation on a
relational benchmark, which leads to discuss possible performance enhancements.
Abstract: The pervasive Internet and the massive deployment of sensor devices
have lead to a huge heterogeneous distributed system connecting millions of data sources and customers together [1].
On the one hand, mediation systems [2] using XML as an exchange language have been proposed to federate data accross distributed heterogeneous data sources.
On the other hand, work [3,4,5,6] have been done to integrate data from sensors.
The challenge is now to integrate data coming from both "classical" data (DBMS, Web sites, XML files) and "dynamic" data (sensors) in the context of an ad-hoc network, and finally, to adapt queries and result to match the client profile.
We propose to use the TGV model [7,8] as a mobile agent to query sources across devices (sources and terminal) in the context of a rescue coordination system.
This work is integrated in the PADAWAN project.
Abstract: Tree Pattern Queries [1,2] are now well admitted for modeling parts of XML Queries.
%Works as GTP [2] use the Tree Pattern Query as a basis to model a part of XQuery specifications.
Actual works only focus on a small subpart of XQuery specifications and are not well adapted for evaluation in a distributed heterogeneous environment.
In this paper, we propose the TGV (Tree Graph View) model for XQuery processing.The TGV model extends the Tree Pattern representation in order to make it intuitive, has support for full untyped-XQuery queries, and for optimization and evaluation. Several types of Tree Pattern are manipulated to handle all XQuery requirements. Links between Tree Patterns are called hyperlinks in order to apply transformations on results.
The TGV, TGV annotations and cost models has been implemented in a mediator system called XLive.
Abstract: This paper presents an efficient evaluation of XQuery in a heterogeneous distributed system.
XQuery(W3C, 2005) is a rich and so a complex language. Its syntax allows us to express a large scale of
queries over XML documents. We have extended (Chen et al., 2003) proposal to rewrite XQuery expressions
in âcanonical XQueryâ in order to support the full XQuery specification.
The XQuery expressiveness makes difficulties to obtain an exclusive internal representation within a system.
Models based on Tree Patterns have been proposed, and we have extended the tree pattern model to a model
called TGV that (a) integrates the whole functionalities of XQuery (b) uses an intuitive representation that
provides a global visualization of the request in a mediation context and (c) provides a support for optimization
and for cost information.
Our paper is based on the XLive mediation system. XLive integrates sources in a uniform view. It is a running
research vehicle designed at PRiSM Laboratory for assessing the integration system at every stage of the
process starting from sources extraction to the user interface and is already used in several projects.
Abstract: Efficient evaluation of XML Query Languages has become a crucial issue for XML exchanges and integration.
Tree Pattern (Sihem et al., 2002; Jagadish et al., 2001; Chen et al., 2003) are now well admitted for representing
XML Queries and a model -called TGV (Travers, 2006; Travers et al., 2006; Travers et al., 2007c)- has
extended the Tree Pattern representation in order to make it more intuitive, respect full XQuery specification
and got support to be manipulated, optimized and then evaluated.
For optimization, a search strategy is needed. It consists in generating equivalent execution plan using extensible
rules and estimate cost of plan to find the better one. We propose the specification of extensible rules that
can be used in heterogeneous environment, supporting XML and manipulating Tree Patterns.
Abstract: Providing services by integrating information available in
web resources is one of the main goals of a mediation architecture. In this
paper, we consider the standard wrapper-mediator architecture under
the following hypothesis: (i) the information exchanged between wrap-
pers and the mediator consists in XML documents, (ii) wrappers have
limited resources, and (iii) to answer queries even if sources are not
available, materialized XML views are stored at the mediator level. In
this setting, we focus on the problem of maintaining materialized XML
views, when the sources change. In our context, wrappers send the up-
dated document without providing any information about the type and
the localization of the update in the document. Then, the problems we
address are, first, identifying the updates, and, second, updating the view
in such a way that accesses to the sources are restricted. Our approach
is based on the XAlgebra, which allows to consider XQuery requests on
XML documents as relational tables. Moreover, our solution uses iden-
tifier annotations for XAlgebra and a diff function.
Abstract: On the Internet, data are distributed on
heterogeneous sources. To integrate them in a
uniform view, lots of systems based on the famous
mediator/wrapper architecture defined by [14] have
been designed [3][12]. The data model now admitted
for representing data is semi-structured data
represented by the XML standard format. Thus now,
as well in industry as in research, integration
systems using XML-based standards have emerged
[5][4].
XLive is such an integration system based on
XML standards. It is the sequels of our experiences
on mediation design in research project (MIROWEB
[11], XML-KM) and in industry XMLMedia.
The XLive prototype is designed to be a light
mediation system with high modularity and
extension capabilities. It is a running research
vehicle designed for assessing the integration system
at every stage of the process starting from sources
extraction to the user interface, including query
parsing and modeling, optimization and evaluation,
and also benchmarking.
Abstract: XQuery is the emerging standard for querying XML data sources. XLive is a light XML/XQuery mediator developed at University of Versailles whose engine processes an XML algebra derived from the relational one extended to process in dataflow XML trees. The query optimizer translates a subset of XQuery in this algebra. To extend the optimizerâs coverage of XQuery and better optimize query plans, we propose a representation of queries as graphs of trees, more precisely as tree pattern graphs interconnected by hyperlinks. Our structure called Tree Graph View (TGV) is an extension of the Generalized Tree Pattern graph proposed in 6 as a concise and practical representation of an XQuery request. It is designed to be a more intuitive model of queries and to allow direct optimization before generating the physical execution plan. TGV lends itself to simple algorithms to generate efficient algebraic execution plans. Moreover, it is effective for view translation and query simplification, and for taking into account source capabilities. We are currently implementing it to support the new XLive optimizer.
Abstract: XML has emerged as the leading language for
representing and exchanging data not only on the Web,
but also in general in the enterprise. XQuery is emerging
as the standard query language for XML. Thus, tools are
required to mediate between XML queries and
heterogeneous data sources to integrate data in XML.
This paper presents the e-XMLMedia mediator, a unique
tool for integrating and querying disparate heterogeneous
information as unified XML views. It describes the
mediator architecture and focuses on the unique
distributed query processing technology implemented in
this component. Further, we evoke the various
applications that are currently being experimented with
the e-XMLMedia Mediator.
Abstract: XML has emerged as the leading language for representing and exchanging data either on the Web or in the enterprise for general purposes. Although XQuery is emerging as the standard for XML query languages, tools are still needed to mediate between XML queries and heterogeneous data sources for the integration of data in XML. This paper presents the XLive mediator, a unique tool for integrating and querying disparate heterogeneous information as unified XML views. It describes the mediator architecture and focuses on the unique distributed query processing technology implemented in this component. Query evaluation is based on an original XML algebra simply extending classical operators to process tuples of tree elements. Further, we present a set of performance evaluation on a relational benchmark, which leads to discuss possible performance enhancements.
Abstract: To cope with the difficulties of Web information search, lots of technologies related to Web search engines have been proposed and have also seen very successful applications. Rather than yet another Web search engines with general purpose, this paper couples text mining and XML view caching techniques within Web mediation architecture and presents a prototype framework for topic-centric Web information search. Given a topic domain, domain-specific information is extracted from the Web documents belonging to the domain, then text-mining technologies are applied to discover the semantics contained in the Web information. Next we integrate the extracted information into a domain-specific common concept model defined using semantic Web languages. Finally an XML-based mediator allows the users to query the integrated Web information using XQuery. Once Web information is represented in the concept model with explicit semantic hierarchy understandable to the programs, user's queries against special fragments of Web documents can be carried out. One important part of our works aims at integrating XML view and cache techniques to manage Web information. Checksum technology is used to monitor the updates of Web page. One prototype is under construction centered on popular French sites of the finance domain.
Abstract: Several federated database systems have been built in the past using
the relational or the object model as federating model. This paper gives an overview
of the XMLMedia system, a federated database system mediator using
XML as federating model, built in the Esprit Project MIRO-Web. The system is
composed of four main components: a wrapper generator using rule-based
scripting to produce XML data from various source formats, a mediator querying
and integrating relational and XML sources, an XML DBMS extender supporting
XML on top of relational DBMSs, and client tools including a Java API
and an XML query browser. The results demonstrate the ability of XML with an
associated query language (we use XML-QL) to federate various data sources
on the Internet or on Intranets.
