Web Service Composition Technologies

1. Web Service Composition Technologies A closer look at WSFL and BPML/WSCI Katharina Siorpaes katharina.siorpaes@deri.at Next Web Generation Seminar SS04 DERI Innsbruck

2. Web Services Composition Technologies 2 Agenda Introduction WSFL BPML/WSCI BPML WSCI Comparison

3. Web Services Composition Technologies 3 How to tap the full potential of … … Web services Multiple invocation between two or more services All parties - Service providers and service clients

4. Web Services Composition Technologies 4 WSFL Web Service Flow Language By IBM To fit into the WS Stack naturally XML-based grammar to describe WS interactions

5. Web Services Composition Technologies 5 Web Services Stack

6. Web Services Composition Technologies 6 Multi-party business processes Operational description ? WSDL (Web Service Description Language) Behavioural description ? WSEL (Web Service Endpoint Description Language) Composition and choreography of WS ? WSFL (Web Service Flow Language)

7. Web Services Composition Technologies 7 Flow Composition in WSFL (I) Choreograph functionalities of a collection of WS Logic of a business process Specification of the execution sequences of the functionalities of services

8. Web Services Composition Technologies 8 Flow Composition in WSFL (II) Business tasks Control flow Data flow

9. Web Services Composition Technologies 9 Global Composition in WSFL Specification of interaction pattern of a collection of WS No specification of execution sequence Interactions between service providers and service requestors Peer-to-peer interactions Hierarchical interactions

10. Web Services Composition Technologies 10 BPML/WSCI ? Complementary efforts Business Process Model Language describes executable business processes private Web Services Choreography Interface describes messages between collaborating web services XML-based language for WS collaboration Public interactions and choreographies between services

11. Web Services Composition Technologies 11 Web Service stack

12. Web Services Composition Technologies 12 BPML XML-based meta-language Developped by Intalio, SUN, SAP, Versata, CSC, SeeBeyond (www.bpmi.org - Business Process Management Initiative) Modeling collaborative and transactional business processes Relying on a formal model

13. Web Services Composition Technologies 13 BPML – 5 elements Activities performance of simple or complex functions Processes types of complex activities that define its own context Contexts environment for the execution of activities Properties information exchange within a context Signals coordination of activities

14. Web Services Composition Technologies 14 BPML key features basic activities for sending, receiving, and invoking services handles conditional, sequential, and parallel activities for Long-running processes supporting persistence supports short and long-running transactions robust exception handling mechanisms Recursive composition No automation support! Services and partners to be specified at design time

15. Web Services Composition Technologies 15 WSCI Defines overall choreography of WS taking part in an interaction BEA Systems, BPMI.org, Commerce One, Fujitsu Limited, Intalio, IONA, Oracle Corporation, SAP AG, SeeBeyond Technology Corporation and Sun Microsystems. Uses messages No focus on the definition of executable business processes (that‘s what BPML does) Direct correspondence to WSDL Each WSCI unit of work ? WSDL operation WSDL: entry points of each service WSCI: interactions among WSDL operations

16. Web Services Composition Technologies 16 WSCI – key features (I) Support for basic activities: each activity specifies the WSDL operation involved use <action> to define a basic request/response message use <call> to invoke external services

17. Web Services Composition Technologies 17 WSCI – key features (II) Support for structured activities: sequential, parallel, and conditional looping use <all> to specify a unordered actions to perform Support for business transactions and exceptions: transactional contexts can be defined in WSCI any failure in a context will result in all transactions in context being rolled back

18. Web Services Composition Technologies 18 WSCI – concepts (I) Interface Observable behaviour of a WS in a message exchange with other WS Activities Basic unit of behaviour; either atomic or complex (composed of other activities) Processes Top-level processes and nested processes Properties Reference a value within an IF definition

19. Web Services Composition Technologies 19 WSCI – concepts (II) Context Environment: a set of activities is executed Message correlation Structure of conversations, management of multiple conversations with the partner Exceptional behaviour Alternative patterns of behaviour; association to activities Transactional behaviour Global model Overall message exchange

20. Web Services Composition Technologies 20 BPEL4WS- BPML BPML is a strict superset of BPEL4WS BPML and BPEL4WS share an identical set of idioms and similar syntaxes as the basis of convergence BPML provides a rich and mature language for expressing both simple and complex business processes

21. Web Services Composition Technologies 21 BPEL4WS – BPML BPML and BPEL4WS are both block-structured languages, with the addition of nested processes in BPML BPML is based on a logical process model that can fully express concurrent, repeating, and dynamic tasks BPML builds on the foundation of WSCI for expressing public interfaces and choreographies

22. Web Services Composition Technologies 22 BPEL4WS – BPLM/WSCI WSCI/BPML has much richer choreography support and backing by W3C working group BPEL4WS has major supporters behind it, with developer tools and documentation already available

23. Web Services Composition Technologies 23 BPEL4WS – BPLM/WSCI

24. Web Services Composition Technologies 24 References V.d. Aalst, W.M.P., Dumas, M., ter Hofstede, A.H.M., Wohed, P. (2002) Pattern-based analysis of BPML (and WSCI), http://xml.coverpages.org/Aalst-BPML.pdf Cabera, F., Copeland, G., Freund, T., Klein J., Langworthy D., Orchard, D., Shewchuk, J., Storey, T. (2002) Web Service Coordination (WS-Coordination), http://www-106.ibm.com/developerworks/library/ws-coor/, 2002 Leymann, F. (2001) Web Services Flow Language (WSFL1.0), http://www-306.ibm.com/software/solutions/webservices/pdf/WSFL.pdf Arkin, A., (2002) Business Process Modeling Language, Arkin, A., Askary, S., Fording, S., Jekeli, W., Kawaguchi, K., Orchard, D., Pogliani, S., Riemer, K., Struble, S., Takacsi-Nagy, P., Trickovic, I., Zimek, S. (2002) Web Service Choreography Interface 1.0

25. Web Services Composition Technologies 25 Thanks for your attention!