WS-BPEL 2.0

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WS-BPEL 2.0
www.oasis-open.org
Web ServicesBusiness Process Execution Language
Workshop Dieter König, IBM Senior Technical
Staff Member (dieterkoenig_at_de.ibm.com) Charlton
Barreto, Adobe Senior Computer Scientist/Architect
(charltonb_at_adobe.com)
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WS-BPEL 2.0
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Abstract
Business Processes not only play a key role in
Business-to-Business (B2B) and Enterprise
Application Integration (EAI) scenarios by
exposing the appropriate invocation and
interaction patterns but they are the fundamental
basis for building heterogeneous and distributed
applications (workflow-based applications). Web
Services Business Process Execution Language
(WS-BPEL) provides the language to specify
business processes that are composed of Web
services as well as exposed as Web services.
Business Processes specified via WS-BPEL are
portable they can be carried out by every
WS-BPEL compliant execution environment. This
presentation gives an overview of the WS-BPEL
language and shows how it can be used to compose
Web services. It provides highlights of WS-BPEL,
including structured activities, correlation,
compensation, and fault handling. Finally, the
OASIS WS-BPEL Technical Committee work, the
current status of the standard, and an outlook on
follow-on activities is presented.
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WS-BPEL 2.0

• Motivation
• OASIS and WS-BPEL
• Main Concepts
• Examples
• Status and support

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Motivation

• Integration continues to be a key problem facing
  businesses
• Intra-enterprise integration (Enterprise
  Application Integration)
• Integrating with partners (Business-to-Business
  Integration)
• Syndication
• Web services ? move towards service-oriented
  computing
• Applications are viewed as services
• Loosely coupled, dynamic interactions
• Heterogeneous platforms
• No single party has complete control
• Service composition
• How do you compose services in this domain?

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Integration
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Concerns addressed by BPEL

• BPEL processes can automate both simple and
  complex interactions between Web services
• Supporting long running business transactions
• Correlating message exchanges
• Implementing parallel processing of activities
• Mapping data between partner interactions
• Providing consistent exception and recovery
  handling

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Why the Need For BPEL?

• WSDL defined Web services have a stateless
  interaction model
• Messages are exchanged using
• Synchronous invocation
• Uncorrelated asynchronous invocations
• Most real-world business processes require a
  more robust interaction model
• Messages exchanged in a two-way, peer-to-peer
  conversation lasting minutes, hours, days, etc.
• BPEL provides the ability to express stateful,
  long-running interactions

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Two programming models

• Programming in the large
• Non-programmers implementing flows
• Flow logic deals with combining functions in
  order to solve a more complex problem (such as
  processing an order)
• Programming in the small
• Programmers implementing functions
• Function logic deals with a discrete fine-grained
  task (such as retrieving an order document or
  updating a customer record)

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Process Usage Patterns

• Aiming for a single approach for both
• Executable processes
• Contain the partners business logic behind an
  external protocol
• Abstract processes
• Define the publicly visible behavior of some or
  all of the services an executable process offers
• Define a process template embodying
  domain-specific best practices

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Process Model Requirements

• Portability and Interoperability
• Flexible Integration
• Rich, and easily adaptable to changes in
  underlying services
• Recursive, type-based composition, enables
• Third-party composition of existing services
• Providing different views on a composition to
  different parties
• Increased scalability and reuse
• Stateful conversations and lifecycle management
• Supports multiple stateful long-running
  conversations
• Recoverability
• Long running business processes need fault
  handling and compensation mechanisms to manage
  and recover from errors

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Benefits of BPEL

• Industry standard language for expressing
  business processes
• Leverage a common skill set and language
• Designed to fit naturally into the Web services
  stack
• Expressed entirely in XML
• Uses and extends WSDL 1.1
• Uses XML Schema 1.0 for the data model
• Portable across platform and vendor
• Will run on any BPEL-compliant engine
• Interoperable between interacting processes
• Layering on top of Web services stack

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WS-BPEL 2.0
BPEL Historical Timeline Dec 2000 Microsoft
publishes XLANG March 2001 IBM publishes
WSFL July 2002 IBM, Microsoft and BEA converge
WSFL XLANG into BPEL4WS 1.0 March 2003 BPEL4WS
is submitted to OASIS May 2003 OASIS publishes
BPEL4WS 1.1 1stH 2007 WS-BPEL 2.0 released

• BPEL is the Web Services Orchestration standard
  from OASIS
• beepel, beepuhl, bipuhl
• An XML-based grammar for describing the logic to
  orchestrate the interaction between Web services
  in a business process

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WS-BPEL in the WS- Stack
WS-BPEL
Business Processes
You are here
WSDL, Policy, UDDI, Inspection
Description
Security
Reliable Messaging
Transactions
Quality Of Service
Coordination
Other protocols
Transport and Encoding
SOAP (Logical Messaging)
Other services
XML, Encoding
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WS-BPEL 2.0

• Motivation
• OASIS and WS-BPEL
• Main Concepts
• Examples
• Status and support

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Getting the Players Together
()
BPEL 1.1
WS-BPEL 2.0
() BPEL 1.1 authors, May 2003
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OASIS Technical Committee

• Charter of the WS-BPEL Technical Committee
• Standardize
• Common concepts for a business process execution
  language for usage patterns including both the
  process interface descriptions and executable
  process models
• Explicitly do not address
• Bindings to specific hardware/software platforms
  and other mechanisms required for a complete
  runtime environment for process implementation
• gt 280 committee members, including observers
• 30 active voting members, attending weekly
  calls
• Issues Process
• List of all issues available at
• http//www.choreology.com/external/WS_BPEL_issues
  _list.html (original list - completed)
• http//www.choreology.com/external/WS_BPEL_review
  _issues_list.html (public review list)

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WS-BPEL Design Goals

• Business processes defined using an XML-based
  language
• Web services are the model for process
  decomposition and assembly
• The same orchestration concepts are used for both
  the external (abstract) and internal (executable)
  views of a business process
• Both hierarchical and graph-like control regimes
  are used, reducing the fragmentation of the
  process modeling space
• An identification mechanism for process instances
  is provided at the application message level
• The basic lifecycle mechanism is in implicit
  creation and termination of process instances.
• A long-running transaction model is defined to
  support failure recovery for parts of
  long-running business processes
• Language built on compatible Web services
  standards in a composable and modular manner

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WS-BPEL 2.0

• Motivation
• OASIS and WS-BPEL
• Main Concepts
• Examples
• Status and support

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WS-BPEL Language Structure

• Process
• Partner links
• Data handling
• Properties and correlation
• Basic and structured activities
• Scopes

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WS-BPEL Process Definition
process
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Relationship with WSDL

• BPEL is layered on top of and extends the WSDL
  service model
• WSDL defines the specific operations allowed
• BPEL defines how WSDL operations are orchestrated
  to satisfy a business process
• BPEL also specifies extensions to WSDL in support
  of long-running asynchronous business processes

BPEL 2.0
WSDL 1.1
BPEL-defined WSDL extensions
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Recursive Composition

• BPEL processes interact with WSDL services
  exposed by business partners

Interfaces exposed by the BPEL process
Interfaces consumed by the BPEL process
Web Service
Web Service
WSDL Loan Approval PortType
Loan Approval Process
receive
Financial Institutions Web Service (Loan
Approver)
invoke
reply
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Composition of Web Services
Service P
Service A
Service B
receive
invoke
receive
invoke
invoke
As WSDL
Ps WSDL
Bs WSDL
F
Partner Link Type
Partner Link Type
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Partner Links
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Variables
process
xsltransform
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Variable Properties
process
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Properties and Correlation Sets
How to identify stateful instances via stateless
Web service interfaces?
process
initiate
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Basic Activities
process
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Structured Activities
process


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Nesting Structured Activities
sequence
ltsequencegt ltreceive .../gt ltflowgt
ltsequencegt ltinvoke .../gt ltwhile
... gt ltassigngt...lt/assigngt
lt/whilegt lt/sequencegt ltsequencegt
ltreceive .../gt ltinvoke ... /gt
lt/sequencegt lt/flowgt ltreply .../gt lt/sequencegt
receive
flow
sequence
sequence
receive
invoke
invoke
while
assign
reply
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Scopes
process
Scopes provide a context which influences the
execution behavior of its enclosed activities
Isolated scopes provide control of concurrent
access to shared resources
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Process Instance Lifecycle

• Business processes defined in BPEL represent
  stateful Web services
• When a process is started, a new instance is
  created according to the process definition
• The creation and destruction of BPEL process
  instances is by design implicit

Process
receive
reply
invoke
invoke
invoke
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WS-BPEL 2.0

• Motivation
• OASIS and WS-BPEL
• Main Concepts
• Examples
• Status and support

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Graph-Oriented Authoring Style
flow
loanApprovalPT
riskAssessmentPT
amount lt 10000
amount gt 10000
receive
loan approver
loan assessor
risk "high"
invoke
invoke
assign
risk "low"
approved "true"
approved "false"
reply
1. A customer asks for a loan, providing name and
amount info 2. Two services are involved a)
A risk assessor which can approve the loan if the
risk is low b) A loan approver which checks
the name and approves/disapproves the loan 3. The
reply is returned to the customer
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Structured Authoring Style
sequence
flow
if-else
if buyer lt seller else
receive (buyer)
assign "failure"
reply (buyer)
reply (seller)
assign "success"
receive (seller)
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Parallel Processing
scope
parallel forEach
flow
. . .
. . .
. . .
. . .
. . .
. . .
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Fault Handling Compensation
Process
fault handler
sequence

notify manager
scope
scope
compensation handler
fault handler
compensate
charge credit card
refund customer
ship goods
rethrow
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Dynamic Partner Link Assignment
Process B
Process A
PortType-B
receive request
invoke service
invoke callback
receive response
PortType-A
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Abstract Executable Processes

• Executable Processes
• Contain the partners business logic behind an
  external protocol
• Model actual behavior of a participant in a
  business interaction
• Encompass enough detail to fully specify execution

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Abstract Executable Processes

• Abstract Processes
• Partially specified processes that are not
  intended to be executed
• May hide some of the required concrete
  operational details
• Serve a descriptive role
• Used to guide executable processes
• More than one possible use case

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Executable Processes View
Travel Reservation - Example
Abstract Process View
Agent Process
Airline Process
Traveler Process
get itinerary
get order
submit to agent
order tickets
receive tickets
receive confirmation
receive confirmation
confirm flight
send tickets
send confirmation
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Abstract Profiles

• Profiles address varying requirements among
  Abstract Processes
• Two profiles provided in WS-BPEL
• Observable Behavior
• Process Template

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Abstract Profiles Use Cases

• Use cases
• Constraints on message exchange
• Specify order in which messages are consumed or
  produced
• View on internal processes
• Only projection of internal (executable) process
  is visible
• Bridge model to executable
• Provide hooks to executable for model definition
  to enable abstraction
• Template as best practice
• Specification of common activities, major data
  structures, and main control flow

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WS-BPEL 2.0

• Motivation
• OASIS and WS-BPEL
• Main Concepts
• Examples
• Status and support

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WS-BPEL

• Portable, interoperable process model for long
  running business processes
• Flexible integration of Web services
• WSDL abstract interfaces alone used to define
  composition
• Enables two levels of adaptive behavior
• Abstract partners can be bound to actual services
  at runtime
• The process can choose a protocol for
  communicating with the service at runtime
• Services whose data definitions do not match can
  be composed
• Data transformations can be inlined in process
  definition

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Whats new since BPEL 1.1?

• Conditional behavior if elseif else
• Replacing the BPEL4WS 1.1 switch activity
• Repetitive execution repeatUntil
• Like BPEL4WS 1.1 while activity with at least one
  iteration
• Processing multiple branches forEach
• Sequential or parallel iteration controlled by a
  counter variable and a completion condition
• Reversing work compensate and compensateScope
• Compensate all child scopes or one specific child
  scope
• Propagating faults rethrow
• Rethrow the fault caught in a fault handler
• Validating data validate
• Explicit XML schema validation of WS-BPEL
  variable content
• Validation also possible within assignment
• Immediately ending a process exit
• Replacing the BPEL4WS 1.1 terminate activity
• Adding new activity types extensionActivity
• Designated WS-BPEL extension point for new
  activity types

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Whats new since BPEL 1.1?

• Variable initialization
• Inline within variable declaration
• Partner links
• Intent for partner role initialization
• Locally declared messageExchange
• Internal correlation of receive/pick/onEvent and
  reply activities
• Correlation sets
• Join behavior for multiple start activities
• XML schema variables in Web service activities
• Usability enhancement for WS-I compliant
  doc/lit-style WS interactions
• Assignment
• Clarification of copy behavior
• Keep source element name
• Ignore missing from data
• Extension assign operation
• XSLT for variable transformations
• New XPath extension function bpeldoXslTransform(
  ...)
• XPath access to variable data
• XPath variable syntax variable.part/location

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Whats new since BPEL 1.1?

• Fault handlers
• XML schema typed fault variables
• Exit on standard fault behavior
• Compensation handlers
• New scope snapshot semantics
• Fault handling during compensation
• Event handlers
• Recurring events
• Resolution of variable, partnerLink,
  messageExchange, correlationSet
• Termination handler
• Customize scope termination behavior
• Import
• Predefined import types WSDL and XSD
• Extensibility
• Global documentation element
• Extension namespace declarations
• Mandatory and optional extensions
• Abstract processes
• Common base (syntax) and profiles (semantics)

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WS-BPEL Adoption Products

• Active Endpoints ActiveBPEL Designer
• Active Endpoints ActiveBPEL Enterprise Server
• BEA WebLogic
• bexee BPEL Execution Engine (open source)
• Cape Clear Orchestrator
• FiveSight Process eXecution Engine (PXE)
• IBM WebSphere Studio Application Developer
  Integration Edition
• IBM WebSphere Business Integration Server
  Foundation
• IBM WebSphere Integration Developer
• IBM WebSphere Process Server
• Microsoft BizTalk Server
• MidOffice BPEL Editor (open source)
• MidOffice BPEL Engine (open source)
• OpenLink Virtuoso Universal Server
• OpenStorm ChoreoServer
• Oracle BPEL Process Manager
• Parasoft BPEL Maestro
• SAP NetWeaver
• SeeBeyond eInsight BPM

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WS-BPEL Application Areas

• Business Process Design
• Autonomic Computing
• Grid Computing
• Semantic Web

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WS-BPEL Schedule

• Status (March 2007)
• First and second public reviews completed
• Approved Committee Specification submitted for
  standardization
• Five organizations have certified use of WS-BPEL
  in product
• ActiveEndpoints, IBM, Intalio, SEEBURGER, Sun

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WS-BPEL Schedule

• Next steps
• OASIS standard - April 2007
• Voting opens March 19 and closes March 30
• OASIS Symposium - April 15-20, 2007San Diego,
  California, USA
• WS-BPEL Lightning Round - April 16
• Business Process Sessions - April 16
• WS-BPEL Workshop - April 18

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WS-BPEL Follow-on Work

• BPEL4People
• Human user interactions
• http//www-128.ibm.com/developerworks/webservices
  /library/specification/ws-bpel4people/
• BPEL Subprocesses
• Based on a coordination protocol
• http//www-128.ibm.com/developerworks/webservices
  /library/specification/ws-bpelsubproc/
• BPELJ
• Inline Java code in activities and
  expressionshttp//www-128.ibm.com/developerworks/
  library/specification/ws-bpelj/
• Currency with related standards
• WSDL 2.0, XPath 2.0, XQuery, etc.

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WS-BPEL Resources

• WS-BPEL 2.0 Committee Specfication (03/2007)
• http//docs.oasis-open.org/wsbpel/2.0/CS01/wsbp
  el-v2.0-CS01.pdf
• OASIS Technical Committee
• http//www.oasis-open.org
• Info aggregator sites
• Wikipedia
• http//en.wikipedia.org/wiki/BPEL
• BPEL Resource Guide
• http//bpelsource.com
• Numerous books and conference papers
• Analyst reports
• BPEL4WS 1.1
• http//www-128.ibm.com/developerworks/library/spec
  ification/ws-bpel/