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BPEL (Business Process Execution Language)

BPEL (Business Process Execution Language). presented by Cagdas E. Gerede 01/24/06 Web Services and Security Seminar UC-Santa Barbara. Adaptation from Nirmal Mukhi’s slides. Business Process Execution Language. enables: Definition of Business Processes using Web Services

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BPEL (Business Process Execution Language)

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  1. BPEL (Business Process Execution Language) presented by Cagdas E. Gerede 01/24/06 Web Services and Security Seminar UC-Santa Barbara Adaptation from Nirmal Mukhi’s slides

  2. Business Process Execution Language • enables: • Definition of Business Processes using Web Services • Coordination of a set of Web service interactions • Degree of interoperability at the process level (describe process and use it in different runtime infrastructures) • where it comes from: • Builds on XML and Web Services • Convergence of two workflow languages (WSFL – directed graphs; XLANG – block-structured language)

  3. Orchestration

  4. Versions • v1.0 - BPEL4WS - August 2002 • v1.1 – March 2003 • v2.0 – Draft - WSBPEL – OASIS • (some issues discussed): • how to use XPath • whether there should be sub-processes in BPEL • how abstract processes should be used

  5. Simple Example Composite Service - Orchestrated by BPEL

  6. Traditional Flow Models Activities represent units of processing. Control links define execution flow as a directed acyclic graph Activities are mapped to application invocations or human actions Flow of data is explicitly modeled through data links.

  7. Structure of a BPEL4WS Process <process ...> <partners> ... </partners> <!-- Web services the process interacts with --> <containers> ... </containers> <!– Data used by the process --> <correlationSets> ... </correlationSets> <!– Used to support asynchronous interactions --> <faultHandlers> ... </faultHandlers> <!–Alternate execution path to deal with faulty conditions --> <compensationHandlers> ... </compensationHandlers> <!–Code to execute when “undoing” an action --> (process body) <!– What the process actually does --> </process>

  8. BPEL Basic Activities <invoke partner=“...” portType=“...” operation=“...” inputContainer=“...” outputContainer=“...”/> <!-- process invokes an operation on a partner: --> <receive partner=“...” portType=“...” operation=“...” container=“...” [createInstance=“...”]/> <!-- process receives invocation from a partner: --> <reply partner=“...” portType=“...” operation=“...” container=“...”/> <!-- process send reply message in partner invocation: --> <assign> <copy> <from container=“...”/> <to container=“...”/> </copy>+ </assign> <!– Data assignment between containers: -->

  9. BPEL and WSDL Partners Partner B Partner A WSDL WSDL A Process Synchronous Communication

  10. Partner A WSDL A BPEL and WSDL. Partners Partner B Asynchronous Communication

  11. Partner Definitions and Links <partner name=“...” serviceLinkType=“...” partnerRole=“...” myRole=“...”/> <!– A partner is accessed over a WS “channel”, defined by a service link type --> <serviceLinkType name=“..."> <role name=“..."> <portType name=“..."/>* </role> <role name=“..."> <portType name=“...”/>* </role> </serviceLinkType> <!– A SLT defines two roles and the portTypes that each role needs to support -->

  12. More Basic Activities <throw faultName=“..." faultContainer=“...“/> <!-- process detects processing error and switches into fault processing mode --> <terminate/> <!– pull the plug --> <wait for=“...”? until=“...”?/> <!-- process execution stops for a specified amount of time--> <empty> <!– Do nothing; a convenience element -->

  13. BPEL Structured Activities <sequence> <!– execute activities sequentially--> <flow> <!– execute activities in parallel--> <while> <!– iterate execution of activities until condition is violated--> <pick> <!– several event activities (receive message, timer event) scheduled for execution in parallel; first one is selected and corresponding code executed. --> <link ...> <!– defines a control dependency between a source activity and a target -->

  14. Nesting Structured Activities. Example <sequence> <receive .../> <flow> <sequence> <invoke .../> <while ... > <assign> ... </assign> </while> </sequence> <sequence> <receive .../> <invoke ... > </sequence> </flow> <reply> </sequence> Seq Flow Seq Seq While

  15. BPEL Critique • No notion of independent activities - everything in a BPEL is a web service operation, not "an activity", i.e. a unit of work • No human interaction modeling • Interacting activities interacting together two-by-two (multiple BPEL documents for a single process) • BPEL can only represent multi-party collaboration that have a "center" of control. (Ariba/CommerceOne - some B2B agent in the middle)

  16. - Questions -

  17. Resources • BPEL4WS 1.0: • http://www-106.ibm.com/developerworks/webservices/library/ws-bpel/ • BPWS4J Java Implementations: • http://www.alphaworks.ibm.com/tech/bpws4j • http://www.collaxa.com/ • Two introductions to BPEL: • http://www.ibm.com/developerworks/webservices/library/ws-bpelcol1 • http://www.ibm.com/developerworks/webservices/library/ws-bpelwp/

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