Business Process Execution Language for Web Services BPEL4WS

1
Business Process Execution Language for Web
Services (BPEL4WS)

• Marcia Perry
• Lawrence Berkeley National Laboratory
• Distributed Systems Department
• May 28, 2004

2
Definition and Purpose

• A language, grammar, or notation for specifying
  business process protocol and behavior based on
  Web Services
• An abstract XML description that exports/imports
  functionality via Web Service interfaces
• Executable language to define control logic for
  coordinating Web Services
• To model business interactions as a workflow
• An aggregation/orchestration of Web services
• Cross-enterprise automated business

3
Types of Processes

• Abstract process (public)
• Business protocol/process definition potential
  execution order of operations from a collection
  of Web services data shared between these Web
  services
• WSDL-based interface operations allowed,
  messages exchanged, partners involved allow
  interoperability between the process and other
  Web services
• Executable process/application (private)
• Model actual behavior of participants in a
  business interaction (e.g., event handling,
  branching)
• Private workflows conveying internal details
  (logic, state)
• Lifecycle

4
WSDL and BPEL

• WSDL interface defines
• Public entry and exit points
• Specific operations allowed
• Data types and messages to describe the
  information that passes between process requests
• BPEL describes how to
• Sequence operations
• Control logic and state
• Coordinate interactions between the process and
  its partners

5
Execution
WSDL 1
WSDL n
6
Related Work

• XLANG WSFL -gt BPEL
• Microsoft XLANG
• Supports sequential, parallel, and conditional
  process flows
• For MS BizTalk Server
• Focuses on creation of business process and
  message exchange between web services

7
Related Work

• IBM Web Services Flow Language (WSFL)
• Defines data exchanges and execution sequence
  (flow model)
• Defines mapping of each step in the flow to
  specific operations
• Grid Services Flow Language (GSFL)
• Specifies workflow descriptions for Grid services
  in OGSA framework
• Based on WSFL

8
WSDL-Based Web Services Stack
9
BPEL Development

• WSDL 1.1, XML Schema 1.0 data model
• XPath 1.0 data manipulation
• Microsoft, IBM, Siebel Systems, BEA Systems, SAP
• Version 1.1 5/03 (supercedes v1.0, 8/02)
• Standardization OASIS Web Services Business
  Process Execution Language TC--current

10
Core Concepts

• Long-running interactions (gt 2 parties)
• Peer-to-peer synchronous/asynchronous message
  exchanges
• Request-response
• One way (e.g., notification, reply to callback
  interface)
• Maintaining state (variables and data access)
• Data-dependent behavior (conditional and timeout
  constructs)
• Exception handling and recovery
• Compensation (reversal of operations)
• Cross-partner coordination (message correlation)

11
Features

• Partner links and roles (model the business
  relationship)
• Sequence vs. parallel flow
• Synchronization of concurrent flows (source and
  target specification)
• Event handlers asynchronous msgs, errors/faults
• Data handling variables, property definition,
  data extraction and assignment
• Scope (group a set of activities)

12
Basic Structure

• ltprocessgt
• ltpartnersgt
• ltpartnerLink namencname myRolencname
• partnerRolencname/gt
• ltvariablesgt
• ltcorrelationSetsgt
• ltfaultHandlersgt
• ltcompensationHandlergt
• lteventHandlersgt
• ltonMessagegt ltonAlarmgt
• ACTIVITIES

13
Basic Activities

• Basic activitiesinstructions that interact with
  an external entity
• receive (incoming message)
• reply (outgoing response or notification message)
• invoke (call a web service)

14
Structured Activities

• Structured activitiesmanage overall process flow
  and define underlying programming logic
• ordering sequence, flow
• conditional looping while
• dynamic branching switch

15
Summary of Constructs

• ltreceivegt
• ltreplygt
• ltinvokegt
• ltvariablegt
• ltassigngt, ltcopygt
• ltcatchgt, ltthrowgt
• ltterminategt
• ltwaitgt
• ltemptygt
• ltsequencegt, ltflowgt

• ltlinksgt, ltlinkgt, ltsourcegt, lttargetgt
• ltswitchgt, ltcasegt, ltotherwisegt
• ltwhilegt
• ltpickgt
• ltonMessagegt
• ltonAlarmgt
• ltscopegt
• ltcompensategt
• ltcorrelationsgt

16
Example

• ltprocess namePurchase targetNamespaceuri
• xmlns ..gt
• ltpartnerLinksgt
• ltpartnerLink nameBuyer
• partnerLinkTypeporequestQuoteLinkType
• myRolePurchaser
• partnerRoleRequester/gt
• ltpartnerLink nameSupplier1
• partnerLinkTypeporequestQuoteLinkType
• myRoleRequester
• partnerRolePurchaser/gt
• ltpartnerLink njameSupplier2 ../gt
• lt/partnerLinksgt

17
Example

• ltvariablesgt
• ltvariable namerequest messageTypeporeq
  uest/gt
• ltvariable namepart_request
  messageTypepopart_request/gt
• ltvariable namepart_quote
  messageTypepopart_quote/gt
• ltvariable nameproposal
  messageTypepoproposal/
• lt/variablesgt
• ltcorrelationSetsgt
• ltcorrelationSet nameQuote
  propertiescorquoteID/gt
• ltcorrelationSet nameProposal
  propertiescorproposalID/gt
• lt/correlationSetsgt

18
Example

• ltfaultHandlersgt
• ltcatch faultNamecantFulfillRequestgt
• ltinvoke partnerLinkBuyer
  operationsendError
• inputVariablefault/gt
• lt/catchgt
• lt/faultHandlersgt

19
Example

• ltsequencegt
• ltreceive namestartBusProcess
  partnerLinkBuyer
• operationrequest variablerequest
  createInstanceyes/gt
• ltflow namesupplier_flowgt
• ltinvoke namequote1 partnerLinkSupplier1
  
• operationrequest_quote
  inputVariablepart_request
• outputVariablepart_quote/gt
• ltinvoke namequote2 partnerLinkSupplier2
  /gt
• lt/flowgt
• ltreply namerespond partnerLinkBuyer
  
• operationsend_proposal
  variableproposal/gt
• lt/sequencegt
• lt/processgt

20
Implementations

• BPWS4J v2.0 (IBM free dist., limited src,
  incomplete implementation, buggy)
• BPWS4J v2.1 (successor to v2.0) will probably go
  commercial
• Collaxa (commercial)
• OpenStorm (commercial)
• GPEL (open source Indiana Univ. Extreme! Lab)
  based on WSRF, WS-Addressing, WS-Notification,
  WS-ReliableMessaging ?

21
PCCE Workflow
22
More Information

• http//www-106.ibm.com/developerworks/webservices/
  library/ws-bpel
• http//www-106.ibm.com/developerworks/library/ws-b
  pelwp
• http//www.alphaworks.ibm.com/tech/bpws4j
• Peltz, C., Web Services Orchestration and
  Choreography, Computer, IEEE, October 2003, pp
  46-52
• Turner, M., Budgen, D., Brereton, P., Turning
  Software into a Service, Computer, IEEE, October
  2003, pp 38-44
• http//www.oasis-open.org/committees/workgroup.php
  ?wg_abbrevwsbpel
• http//www.collaxa.com/
• www.extreme.indiana.edu/swf-survey/
  GGF10_bpel_in_grids-2004-03-10.ppt
• http//www.extreme.indiana.edu/groc/ggf10-ww/index
  .html