Active XML

XML and Web Services provide standards for accessing more and more sources of dynamic, up-to-date, relevant information.

Active XML (AXML for short) is a declarative framework that harnesses web services for data integration, and is put to work in a peer-to-peer architecture.

A description of the first years of the AXML project can be found here.

The AXML work has been partially funded by the EU projects DBGlobe and Edos and the French government grants ACI MDP2P and ANR DocFlow.

News

AXML Fundamentals

Active XML documents are XML documents that may include embedded calls to Web services. Hence, AXML documents are a combination of regular extensional XML data with data that is defined intensionally, i.e., as a description that enables obtaining data dynamically (by calling the corresponding service).

AXML documents evolve in time when calls to their embedded services are triggered. The calls may bring data once (when invoked) or continually (e.g., if the called service is a continuous one, such as a subscription to an RSS feed). They may even update existing parts of the document (e.g., by refreshing previously fetched data).

AXML documents

An AXML document is a (syntactically valid) XML document, where service calls are denoted by special XML elements labeled call. An example AXML document is given below. The figure shows first the XML serialized syntax, then a more abstract view of the same document as a labeled tree. The document in the figure describes a (simplified) newspaper homepage consisting of (i) some extensional information (the name of the newspaper, the current date, and a news story), and (ii) some intensional information (service calls for the weather forecast, and for the current exhibits). When the services are called, the tree evolves. For example, the tree at the bottom is what results from a call to the service f at weather.com to obtain the temperature in Paris.

                         
 <?xml version="1.0" encoding="UTF-8" ?>
<newspaper xmlns="http://lemonde.fr"
	xmlns:rss="http://purl.org/rss"
	xmlns:axml="http://axml.net">
	<title>Le Monde</title>
	<date>2008/3/12</date>
	<story>Today...</story>
	<weather>
		<axml:call service="f@weather.com" >
			<location>Paris</location>
		</axml:call>
	</weather>
	<shows>
		<axml:call service="events@timeout.com">
			<city>Paris</city>
		</axml:call>
	</shows>
</newspaper>
 

NOTE: The above presented syntax is written from a scientific point of view, for a better understanting of the principles behing Active XML. For the syntax of an AXML document, version 2.0, please refer to documentation.

Documents Exchange

When exchanged between two applications/peers, AXML documents have a crucial property: since Web services can be called from anywhere on the Web, data can either be materialized before sending, or sent in its intensional form and left to the receiver to materialize if and when needed.

Query evaluation

Answering a query on an AXML document may require triggering some of the service calls it contains. These services may, in turn, query other AXML documents and trigger some other services, and so on. This recursion, based on the management of intensional data, leads to a framework in the style of deductive databases.

Efficient query processing is, in general, a critical issue for Web data management. AXML, when properly extended, becomes an algebraic language that enables query processors installed on different peers to collaborate by exchanging streams of (A)XML data. The crux of the approach is (i) the introduction of generic services (i.e., services that can be provided by several peers, such as query processing) and (ii) some explicit control of distribution (e.g., to allow delegating part of some work to another peer).

Key applications

AXML and the AXML algebra target all distributed applications that involve the management of distributed data. AXML is particularly suited for data integration (from databases and other data resources exported as Web services) and for managing (active) views on top of data sources. In particular, AXML can serve as a formal foundation for mash-up systems. Also, the language is useful for (business) applications based on evolving documents in the style of business artifacts, and on the exchange of such information. The fact that the exchange is based on flows of XML messages makes it also well-adapted to the management of distributed streams of information.

Implementation

The implementation of Active XML peers done in Java, and relies on the following software:

• Apache Tomcat 5.5 servlet engine,
• Apache Axis2 Web services engine,
• eXist native XML database.

Publications

Journal articles

Serge Abiteboul, Omar Benjelloun, Tova Milo: The Active XML project: an overview, VLDB Journal 2008 (pdf).

Conference papers, posters & demos

S. Abiteboul, T. Allard, P. Chatalic, G Gardarin, A. Ghitescu, F. Goasdoué, I. Manolescu, B.Nguyen, M. Ouzara, A Somani N. Travers, G. Vasile and S. Zoupanos WebContent: Efficient P2P Warehousing of Web Data, VLDB 08, Auckland, New Zealand, August 2008 (pdf).

Il-Gon Kim, Debmalya Biswas: Application of Model Checking to AXML System's Security: A Case Study, 3rd International Workshop on Web Services and Formal Methods, Vienna, Austria, September 2006 (pdf).

Emanuel Taropa, Won-Jong Lee, Tack-Don Han: Fast Obtaining Weak Code Mobility Using Active XML, Proc. of Korea Computer Congress 2005 (to appear) (pdf).

Serge Abiteboul, Ioana Manolescu, Nicoleta Preda: Constructing and querying peer-to-peer warehouses of XML resources, International "Semantic Web and Databases" workshop (in cooperation with the VLDB conference) Toronto, Canada, August 2004 (ps).

S. Abiteboul, Z. Abrams, S. Haar, T. Milo: Diagnosis of Asynchronous Discrete event systems. Datalog to the rescue!, PODS, 2005 (pdf)

Nicolaas Ruberg, Gabriela Ruberg, Ioana Manolescu: Towards cost-based optimization for data-intensive Web service computations, SBBD International Conference, Brasilia, Brazil, October 2004 (conference version (ps) Extended version: INRIA Research report no 5222, June 2004 (ps)).

Serge Abiteboul, Bogdan Alexe, Omar Benjelloun, Bogdan Cautis, Irini Fundulaki, Tova Milo, Arnaud Sahuguet: An Electronic Patient Record "on Steroids": Distributed, Peer-to-Peer, Secure and Privacy-conscious, VLDB 2004 (pdf).

Etienne Canaud, Salima Benbernou, Mohand-Saïd Hacid: Managing Trust in Active XML , SCC 2004 (pdf).

Serge Abiteboul, Omar Benjelloun, Tova Milo: Positive Active XML, PODS 2004 (pdf).

Serge Abiteboul, Omar Benjelloun, Bogdan Cautis, Ioana Manolescu, Tova Milo, Nicoleta Preda: Lazy Query Evaluation for Active XML, SIGMOD 2004 (pdf).

Anca Muscholl, Thomas Schwentick, Luc Segoufin: Active Context-Free Games, STACS 2004 (ps).

Serge Abiteboul, Jerome Baumgarten, Angela Bonifati, Grégory Cobena, Cosmin Cremarenco, Florin Dragan, Ioana Manolescu, Tova Milo, Nicoleta Preda: Managing Distributed Workspaces with Active XML, VLDB 2003 (demo) (pdf).

Serge Abiteboul, Bernd Aman, Jerome Baumgarten, Omar Benjelloun, Frederic Dang Ngoc, Tova Milo: Schema-driven Customization of Web Services, VLDB 2003 (demo) (pdf).

Tova Milo, Serge Abiteboul, Bernd Amann, Omar Benjelloun, Frederic Dang Ngoc: Exchanging Intensional XML Data, SIGMOD 2003 (ps).

Serge Abiteboul, Angela Bonifati, Gregory Cobena, Ioana Manolescu, Tova Milo: Dynamic XML Documents with Distribution and Replication, SIGMOD 2003 (ps).

Serge Abiteboul, Grégory Cobena, Benjamin Nguyen, Antonella Poggi: Construction and Maintenance of a Set of Pages of Interest (SPIN), BDA 2002.

Serge Abiteboul, Omar Benjelloun, Ioana Manolescu, Tova Milo, Roger Weber: Active XML: Peer-to-Peer Data and Web Services Integration. VLDB 2002 (demo)(ps).

Serge Abiteboul, Omar Benjelloun, Tova Milo, Ioana Manolescu, Roger Weber: Active XML: A Data-Centric Perspective on Web Services, BDA 2002 (ps).

Serge Abiteboul, Omar Benjelloun, Tova Milo: Towards a Flexible Model for Data and Web Services Integration, FMII workshop, 2001.

Abstracts and full papers can also be obtained from the Gemo publication server.

Presentations

Spyros Zoupanos: OptimAX (pdf).

Serge Abiteboul: Active XML (pdf).

Omar Benjelloun: Active XML at IRISA, september 27th, 2002 (HTML slides + video in french).

Angela Bonifati: Dynamic XML Documents with Distribution and Replication, SIGMOD 2003 (ppt).

Omar Benjelloun: Exchanging Intensional XML Data, SIGMOD 2003 (ppt).

PhD dissertations and internship reports

Omar Benjelloun: Active XML: A data centric perspective on Web services, PhD dissertation, 2004 (ps).

Cosmin Cremarenco: Implementation of the Active XML Peer for the J2ME platform, 2003 (pdf).

Shobhit Raj Mathur: Exchanging Intensional XML Data, 2003 (ps).

Emanuel Taropa: Continuous and Composed Services in Active XML, 2004 (pdf).

Bogdan-Eugen Marinoiu: Development environment for dynamical Web data, 2004 (pdf).

Sandeep Gupta: Cost Optimization of Service Call Materialization,2005 (doc).

For a list of open issues for axml, please consult Open issues