1 Serge Abiteboul – Singapore Web services and data integration S. AbiteboulOmar Benjelloun Tova Milo INRIA and Xyleme INRIAINRIA and Tel Aviv Singapore, December 2002

2 Serge Abiteboul – Singapore Organization The context Accessing information on the Web Web services –SOAP –WSDL –UDDI Active XML –AXML documents –AXML services Architecture et implementation Applications Conclusion

3 Serge Abiteboul – Singapore The context The Web and XML are changing dramatically the management of distributed information

4 Serge Abiteboul – Singapore Distributed data management Warehousing Mediation Management of data in cooperative work Management of data in distributed scientific applications Mobile data management Document management Web sites Portals, etc. Information used to live in islands and this is changing

5 Serge Abiteboul – Singapore The Web of yesterday Protocol: HTTP Documents: HTML Millions of independent Web sites and billions of documents Browsing and full-text indexing Publication of databases using forms Data management with the Web –HTML is primarily to be read by humans –Data management applications over Web data Based on hand-made wrappers Expensive, incomplete, short-lived, not adapted to the Web constant change No real support for distributed data management!

6 Serge Abiteboul – Singapore Information used to live in islands but it is changing Different formats: relational, metadata, documents, text, DXF –A Web standard for data exchange, XML, is fixing it –XML captures all kinds of information over a wide spectrum –XML comes with a family of emerging standards: XML schema, XSL/T, Xquery, domain specific schemas… Different computers, platforms, languages, applications –A standard for Web services, SOAP, is fixing it –SOAP allows ubiquitous computing on the Internet –SOAP comes with a family of emerging standards: WSDL, UDDI This provides a uniform access to information… …the dream for distributed data management

7 Serge Abiteboul – Singapore The information spectrum Structured Data Minimal structure Meta dataHierarchy + BooksContractsCatalogs Bank accounts s Financial Reports Insurance Policies Economical Analysis Derivatives Inventory Political analysis Insurance Claims Financial NewsSports News Resumes Semi-structured data and XML

8 Serge Abiteboul – Singapore What can be captured with XML? Very structured information such as database, knowledge base –Most DBMS now export in XML Semi-structured data such as data exchange formats (ASN.1, SGML), e.g., technical documentation Less structured data: documents –Meta-data: Author, date, status –Existing structure in them: chapter, section, table of content and index –Possibly tagging of elements in it (citation, lists) –Links to other documents Plain text Meta data for unstructured data such as images and sound

9 Serge Abiteboul – Singapore A standard for information: XML labeled ordered trees where leaves are text Marriage of document and database worlds Marriage of full text indexing and structure indexing Is it the ultimate data model? No Purely syntax – more semantics needed Is it OK for now? Definitely yes (because it is a standard)

10 Serge Abiteboul – Singapore The main asset of XML: typing Applications need typing and XML data can be typed if needed (DTD and XML schema) Trees Logical Granularity – neither page or document level – but the piece of information that is needed Semantics and structure are in tags and paths –product-table/product/reference –product-table/product/price product designation description price reference product-table

11 Serge Abiteboul – Singapore A standard for distributed computing: Web services Possibility to activate a method on some remote Web server Exchange information in XML: input and result are in XML Ubiquitous XML distributed computing infrastructure 2 main applications –E-commerce –Access to remote data With XML and Web services, it is possible –To get information from virtually anywhere –To provide information to virtually anywhere

12 Serge Abiteboul – Singapore The basic picture Black box m( ) SOAP messages answer Internet Web client XML SOAP service query

13 Serge Abiteboul – Singapore Accessing and integrating information

14 Serge Abiteboul – Singapore Accessing remote information Application using gene banks Query some data services that provide candidate genes Gene banks processing Use some processing services Multi formats + multi protocoles

15 Serge Abiteboul – Singapore Same with Web services Query some data services that provide candidate genes Gene banks processing Use some processing services Web Application using gene banks

16 Serge Abiteboul – Singapore The big picture: peer2peer Web queries Web service Web service Data warehouses Databases Web pages PC, PDA, cell phones… … DB Web Service DB Web Service queries

17 Serge Abiteboul – Singapore The main roles Client Service Provider Service Registry publish bind Look up

18 Serge Abiteboul – Singapore Simple view: Looking for information about Gismos 1.Query some yellow-pages: Who knows about Gismos? 1.Negotiate with Gismo specialists Nature of the service Quality, cost 2.Get the information Order, payment, delivery Integration in my information system 3.Eventually publish information 4.… and all this automatically…

19 Serge Abiteboul – Singapore Data integration – Logical view Mediator or warehouse Service directories Service descriptions Get service description source1 source2source3 wrapper1 wrapper2 wrapper3 Ontologies Find ontologies to build wrappers

20 Serge Abiteboul – Singapore The Web service solution Web UDDI RDF wsdl XML+SOAP wsfl Data and service description worklow Data and service repository Data and service semantics

21 Serge Abiteboul – Singapore Mediation with Web services Mediator source1 source2 source3 wrapper1 wrapper2 wrapper3 Web Web services: Service directories Service descriptions Wrappers Sources Mediators/warehouses Service directories Service descriptions

22 Serge Abiteboul – Singapore Advantages for data integration A universal model for data integration = XML –Solves the heterogeneity issue A universal protocol for distribution = SOAP A language for describing the interface of data sources = WSDL –Simple object access protocol (something like Corba) –Web service description language (something like IDL) –Solves the interoperability issue A standard for publication and discovery of information = UDDI –Universal Description, Discovery and Integration A standard for describing the semantics of sources = RDF –Resource description framework

23 Serge Abiteboul – Singapore Advantages – continued – the goal The system can find a new source of information using UDDI Understand its syntax using WSDL Understand its semantics using RDF Get it using SOAP The information is in XML, can be restructured and integrated automatically Not yet… But soon?

24 Serge Abiteboul – Singapore Jargon XML XHTML RDF.NET RosettaNet WSFL DTD Xschema XSL XSLT XSL-FO ebXML namespace HTTPS OASIS HTTP SOAP OAGIS WSDL ICE RSS UDDI WSDL MIME Help!

25 Serge Abiteboul – Singapore Active XML Joint work with: Bernd Amann, Jerôme Baumgarten, Angela Bonifati, Ioana Manolescu, Frederic Ngoc and others

26 Serge Abiteboul – Singapore q1($1,$2), Q2, Q3… (XPATH, Xquery) AXML = XML + embedded SOAP calls AXML Internet AXML peer: client and server Web server m( ) SOAP messages answer AXML query Internet answer query Web client

27 Serge Abiteboul – Singapore Active XML Peer-to-peer architecture Each Active XML peer –Repository: manages active XML data with embedded Web service calls –Web client: activate calls in the documents –Web server: provides Web services defined as (parameterized) queries over the repository AXML peer soap

28 Serge Abiteboul – Singapore Build on existing standards Tree data: XML –internal data representation and –data exchange Web services: SOAP, WSDL Query languages: Xquery/Xpath AXML XML

29 Serge Abiteboul – Singapore AXML peer: repository of AXML documents toy.xyz.com/GetToyPersonel() dvd2000.com/GetDVDPersonnel() Service calls May contain calls to any SOAP Web service e-bay.net, google.com, etc. to any AXML Web service

30 Serge Abiteboul – Singapore AXML peer: Web client 01… toy.xyz.com/GetToyPersonel() dvd2000.com/GetDVDPersonnel() Result

31 Serge Abiteboul – Singapore Controlling the evaluation Activation of calls and data lifespan are controlled –frequency: when is the service called ? (« call each day ») – validity: how long is the retrieved data valid ? – mode: immediate or lazy ?

32 Serge Abiteboul – Singapore Example: control attributes toy.xyz.com/GetToyPersonel() dvd2000.com/GetDVDPersonnel()

33 Serge Abiteboul – Singapore AXML peer: Web server AXML Web services: defined using XQuery over AXML documents let service Get-Toy-Personnel( ) be for $a in document("toy.xyz.com/members.axml")/member, $b in $a//name, $c in $a//phone, $d in $a//pda return { $c } { $d }

34 Serge Abiteboul – Singapore The crux: the exchange of AXML data Arguments & result of calls are AXML Data is thus intentional & dynamic Distributed computing: by sending data containing service calls, one can delegate some work to other peers Partial computations: by returning data containing service calls, one can give to the receiver the control of these calls All this can be controlled

35 Serge Abiteboul – Singapore Example: Tourist guide … yahoo.com/Temp(“Paris”) … I need to evaluate the temperature of Paris 1.I call Yahoo: meteoF.com/t(“Paris”) 2.I call meteoF: 0 I am asked what is the temperature of Paris … 0 … meteoF.com/t(“Paris”) … … yahoo.com/Temp(“Paris”) …

36 Serge Abiteboul – Singapore Continuous services Inside the tourist guide: new events Pull mode : standard SOAP query –Ask once a week Push mode : subscription to a continuous service –When new events are announced, they are pushed to the AXML document Possibility to define AXML continuous services

37 Serge Abiteboul – Singapore Architecture and implementation

38 Serge Abiteboul – Singapore Global architecture XQuery processor Evaluator query service descriptions read update read update consults SOAP wrapper SOAP AXML peer S3 SOAP service SOAP client AXML peer S1 service callservice result AXML document store AXML peer S2 AXML XML AXML

39 Serge Abiteboul – Singapore Implementation SUN’s Java SDK 1.4 (includes XML parser, XPath processor, XSLT engine) Apache Tomcat 4.0 servlet engine Apache Axis SOAP toolkit 1.0 beta 3 X-OQL query processor, persistent DOM repository JSP-based user interface, using JSTL 1.0 standard tag library First prototype –No lazy evaluation –No continuous services On going work on typing, security, replication… Demo for VLDB’02 –P2P auctioning system

40 Serge Abiteboul – Singapore Illustration: 3 applications

41 Serge Abiteboul – Singapore Application 1: Warehousing Construction of warehouses with Web data Monitoring of changes on the Web Kind of services that are used –Google search engine –wget –Classification –XML Diff and site changes –Page monitoring system –etc.

42 Serge Abiteboul – Singapore Application 2: Mobile data AXML peers as mobile entities Active data store with query capabilities –Metadata and object profiles Issues –Storage services for mobile objects –Processing services for mobile objects –Use proxies for that European Project DBGlobe

43 Serge Abiteboul – Singapore Application 2: Mobile data Light-weight AXML peers –PDA, cellular phone, laptop… –Limited storage, network bandwidth –Sometime disconnected Limited functionalities –E.g., support for continuous services based on a mail server and SMTP

44 Serge Abiteboul – Singapore Application 2 : context awareness Where am I? (geographical position) Where is the « nearest » AXML proxy? (network position) Active use of this information –For providing context dependent data (e.g., time, temperature, nearest restaurants, etc.) –For selecting services (e.g., choose a nearby proxy for caching)

45 Serge Abiteboul – Singapore Application 3: P2P Auction Each peer proposes some auctions –The document records the peer’s items and the bids Each peer knows about some auctions of other peers Each peer can bid on any auction –The peer recalls the bids she has put When an auction closes, the winner is notified No centralization

46 Serge Abiteboul – Singapore Conclusion and on-going work

47 Serge Abiteboul – Singapore AXML services A simple, declarative way to create Web services compatible with current standards for Web services invocation AXML services are powerful tools for data integration They allows for new, powerful features Intentional parameters and results: AXML documents (containing service calls) that are exchanged. Continuous services send back a stream of answers (SOAP messages) to the caller

48 Serge Abiteboul – Singapore Many issues Security Typing of parameters Lazy evaluation and optimization Replication Mobility: dbglobe project Termination Implementation Foundations And more

49 Serge Abiteboul – Singapore Security Peers exchange AXML documents containing service calls A server (resp. client) might ask the client (resp. server) to do something « bad »: qod.com/QuoteOfDay My heart was bumping Tskitishvili, picked 5th in the NBA draft by the Denver Nuggets buy.com/BuyCar(« BMW Z3 »)

50 Serge Abiteboul – Singapore Using type to control the use of services Peer1 Peer2 fg Evaluate g before sending data f Accept Peer1 tells which kind of data it exports and Peer2 which kind it accepts

51 Serge Abiteboul – Singapore Distribution and replication Motivated by mobile devices with limited resources Allows to distribute one XML document on several peers Allows to replicate an XML-sub-tree on several peers Query optimization

52 Serge Abiteboul – Singapore Thanx more questions: