1. XML.gov Working Group Washington, DC February 18, 2004 Introduction to Business Process Execution Language for Web Services (BPEL4WS) Joseph M. Chiusano Booz | Allen | Hamilton

2. 1 Overview  Introduction  Partner Links  Main BPEL4WS Process Flow Constructs  Message Correlation  Process Compensation  Questions

3. 2 Introduction

4. 3 BPEL4WS (Business Process Execution Language For Web Services) provides a language for the formal specification of business process behavior based exclusively on Web Services  BPEL4WS extends the Web Services interaction model and enables it to support business transactions  It defines a model and grammar for describing the behavior of a business process based on interactions between the process and its partners  The BPEL4WS specification was originally authored by IBM, Microsoft, BEA Systems, SAP, and Siebel Systems  The most current public version is Version 1.1 (May 2003) http://www-106.ibm.com/developerworks/webservices/library/ws-bpel/  The OASIS WS BPEL Technical Committee is advancing the BPEL4WS Specification  Updated version planned for release in February/March 2004

5. 4 BPEL4WS sits at the top of the emerging Web Services stack, at the “process/collaboration modeling” layer  BPEL4WS sits above Web Services Choreography definitions BPEL4WS Process/Collaboration Modeling Definitions Web Services Choreography Definitions Current Web Services Stack WSCI, W3C Web Services Choreography WSDL, SOAP, Messaging, Discovery, etc.

6. 5 The BPEL4WS process model is layered on top of the service model defined by WSDL 1.1  WSDL specifies a hierarchy for describing Web Services characteristics in an abstract form: Operations Ex: Purchase Order Status Query Port Type (“Interface” in 2.0) Ex: Purchase Order Interface Messages Ex: Submit Purchase Order Number, Receive Status Parts Ex: Purchase Order Number, Status

7. 6 BPEL4WS is capable of modeling complex business processes, and the dependencies between activities  The following is a BPEL4WS process for handling a purchase order: Source: BPEL4WS Version 1.1 Specification “Production Scheduling” portType “Shipping Services” portType “Invoice Services” portType “Purchase Order” portType operation message <portType name=“schedulingPT” “Initiate Production Scheduling” operation “Complete Production Scheduling” operation

8. 7 Partner Links

9. 8 Partner links are used to represent interactions between a service and each of the parties with which it interacts  Partner links define the messages and port types used in the interactions in both directions, along with role names “Shipping” partner link “Invoicing” partner link “Scheduling” partner link “Purchasing” partner link <partnerLink name="scheduling" partnerLinkType="lns:schedulingLT" partnerRole="schedulingService"/> The portType used in the partner link

10. 9 Main BPEL4WS Process Flow Constructs

11. 10 The “receive”, “flow” and “reply” constructs are the main BPEL4WS constructs used to represent process flows  The purchase order example uses all three constructs “Receive” construct “Flow” construct “Reply” construct

12. 11 The “receive”, “flow” and “reply” constructs are the main BPEL4WS constructs used to represent process flows (cont’d)  The receive construct allows a process to do a blocking wait for a matching message to arrive <receive partnerLink="purchasing" portType="lns:purchaseOrderPT" operation="sendPurchaseOrder" variable="PO">  The flow construct allows one or more activities to be performed concurrently Source: SOAP 1.1 Recommendation Wait to receive a purchase order on the “Purchasing” partner link Represents the purchase order message

13. 12  The reply construct allows a process to send a message in reply to a message that was received through a <reply partnerLink="purchasing" portType="lns:purchaseOrderPT" operation="sendPurchaseOrder" variable=“Invoice"> Source: SOAP 1.1 Recommendation Send invoice on the “Purchasing” partner link Represents the invoice message The “receive”, “flow” and “reply” constructs are the main BPEL4WS constructs used to represent process flows (cont’d)

14. 13 BPEL4WS is also capable of modeling dependencies between activities  There are several dependencies in the purchase order example Source: BPEL4WS Version 1.1 Specification Cannot complete price calculation until shipper is determined Cannot complete production scheduling until shipping logistics are arranged

15. 14 The synchronization dependencies between concurrent tasks are expressed by using “links” to connect them  The following represents the dependency of the price calculation on the shipper selected: <invoke partnerLink=“shipping" portType="lns:shippingPT" operation=“requestShipping" inputVariable="shippingRequest"> outputVariable="shippingInfo"> <invoke partnerLink=“invoicing" portType="lns:computePricePT" operation=“sendShippingPrice" inputVariable="shippingInfo"> This represents the “Decide on Shipper” activity This represents the “Complete Price Calculation” activity The common link name represents a dependency between the two activities

16. 15 Message Correlation

17. 16 Message correlation involves the association of two or more messages with each other in an asynchronous environment Source: SOAP 1.1 Recommendation  This may be done by associating contents in a given message with its correlating message  For example, in a purchase order/invoice scenario, the invoice may contain the corresponding purchase order number........ Purchase Order:........ Invoice: Purchase order number is common in both messages

18. 17 BPEL4WS represents message correlations using “correlation sets”  A correlation set contains a set of properties shared by all messages in a correlated group <invoke partnerLink="Buyer" portType="SP:BuyerPT" operation="AsyncPurchaseResponse" inputVariable="POResponse"> <correlationSet name="PurchaseOrder" properties="cor:customerID cor:orderNumber"/> <correlationSet name="Invoice" properties="cor:vendorID cor:invoiceNumber"/> Declares correlation between purchase order and invoice A customer ID and order number represent a unique purchase order A vendor ID and invoice number represent a unique invoice

19. 18 Endpoint References

20. 19 BPEL4WS uses “endpoint references” for dynamic selection of service providers and invocation of their operations  The relevant information about a partner service can be set up as part of business process deployment  This is a more “static” approach  However, it is also possible to select and assign partner services dynamically  BPEL4WS leverages the WS-Addressing specification for this capability  WS-Addressing defines a standard representation for endpoint references that incorporates information from a WSDL description as well as policy information: http://www.someendpoint.com PurchaseOrderPortType  URL: http://msdn.microsoft.com/ws/2003/03/ws-addressinghttp://msdn.microsoft.com/ws/2003/03/ws-addressing The portType associated with the address

21. 20 Process Compensation

22. 21 Business processes are often of long duration, which means that a business process may need to be cancelled after many transactions have been committed during its progress Sub mit Pur cha se Ord er Pro ces s Pur cha se Ord er Che ck Inve ntor y Ord er Fro m Sup plie r User Cancels!  Consider a situation in which a user cancels a purchase order:  In this situation, it is not possible to lock system resources (ex: database records) for extended periods of time  Therefore, the partial work must be undone as best as possible Revert back to original state

23. 22 BPEL4WS defines “compensation handlers” that are invoked to perform compensation activities  A compensation handler is essentially a “wrapper” for compensation activities  Specifies a compensating operation on a given portType for a given partner link: <invoke partnerLink="Seller" portType="SP:Purchasing" operation="CancelPurchase" inputVariable="getResponse" outputVariable="getConfirmation"> <correlation set="PurchaseOrder" pattern="out"/> The “CancelPurchase” operation invokes a cancellation The response to the purchase request is used as input

24. 23 Questions?

25. 24 Contact Information Joseph M. Chiusano Booz | Allen | Hamilton McLean, VA (703) 902-6923 chiusano_joseph@bah.com