1. WS-BPEL 2.0 Web Services Business Process Execution Language Workshop
WS-BPEL 2.0
Web Services Business Process Execution Language Workshop
Dieter König, IBM Senior Technical Staff Member
Charlton Barreto, Adobe Senior Computer Scientist/Architect

2. WS-BPEL 2.0 Variables Basic Partner Activities Links Structured42
WSDL Message
XML Schema
Type
Element
Basic
Activities
receive
reply
invoke
throw
exit
wait
empty
compensate
validate
assign
rethrow
extensionActivity
compensateScope
Partner
Links
Link Type
Port
Type 1
Type 2
partner
link
WS-BPEL 2.0
MyProcess
invoke
receive
Structured
Activities
if-else
while
scope
pick
sequence
flow
repeatUntil
forEach
Handlers
fault
handler
event
compensation
termination
Properties
Correlation Sets
Property 1
Property 2

3. 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.

4. Motivation OASIS and WS-BPEL Main Concepts Examples Status and support

5. 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?

6. Integration

7. 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

8. 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

9. 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)

10. Process Usage Patterns
Aiming for a single approach for both
Executable processes
Contain the partner’s 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

11. 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
Portability and Interoperability
Flexible Integration
Rich, and easily adaptable to changes in the services it is interacting with
Recursive, type-based composition, enables …
third-party composition of existing services
providing different views on a composition to different parties
inter-workflow interaction
increased scalability and reuse
Separation and composability of concerns
Decoupled from the supporting mechanisms (quality of service, messaging frameworks)
Stateful conversations and lifecycle management
Can carry multiple stateful long-running conversations
Recoverability
Business processes, and in particular long running ones, need a way to build-in fault handling and compensation mechanisms to handle and recover from errors

12. 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
WS-BPEL enables …
Defining business processes as coordinated sets of Web service interactions, recursively into new aggregated Web services
Defining both abstract and executable processes
Abstract processes for e-commerce specifications
Executable processes provide a model to integrating enterprise applications
Creating compositions of Web services
Composition based on abstract descriptions
WS-BPEL provides portable, interoperable process models
WS-BPEL comes from …
Strong roots in traditional flow models
Plus many concepts from structured programming languages
All laid on top of WSDL and core XML specifications
Merges WSFL and XLANG concepts

13. WS-BPEL 2.0 BPEL is the Web Services Orchestration standard from OASIS
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
bee•pel’, beep’•uhl, bip’•uhl
An XML-based grammar for describing the logic to orchestrate the interaction between Web services in a business process
BPEL was first released on July 2, 2002, as BPEL4WS V1.0, jointly by BEA Systems, Inc., IBM Corporation, and Microsoft Corporation. BPEL4WS
Version 1.0 merges the flat-graph process definition approach of IBM’s Web Services Flow Language (WSFL) with the structural constructs approach of Microsoft’s XLANG. In 2003, BPEL4WS 1.1 was released with a set of revisions and an expanded list of authors; it is the version of the specification that was submitted to OASIS.
OASIS is currently working on producing the standardized version of the language, known as WS-BPEL 2.0.

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

15. Motivation OASIS and WS-BPEL Main Concepts Examples Status and support

16. Getting the Players Together
(*)
BPEL 1.1
WS-BPEL 2.0
(*) BPEL 1.1 authors, May 2003

17. 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
> 280 committee members, including observers
~ 30 active voting members, attending weekly calls
Issues Process
List of all issues available at
(original list - completed)
(public review list)

18. 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

19. Motivation OASIS and WS-BPEL Main Concepts Examples Status and support

20. WS-BPEL Language Structure
Process
Partner links
Data handling
Properties and correlation
Basic and structured activities
Scopes

21. WS-BPEL Process Definition
imports
Declare dependencies on external XML Schema or WSDL definitions
extensions
Declare namespaces of WS-BPEL extension attributes and elements
partner
links
Relationships that a WS-BPEL process will employ in its behavior
message
exchanges
Relationship between inbound and outbound message activities
variables
Data holding state of a business process or exchanged with partners
correlation
sets
Application data fields that together identify a conversation
event
handlers
Concurrently process inbound messages or timer alarms
fault
handlers
Deal with exceptional situations in a process
Elements of a process definition
primary
activity
Perform the process logic – any number of activities may be recursively nested
XML
schemas
WSDL
definitions

22. 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 processes are exposed as WSDL services
Message exchanges map to WSDL operations
WSDL can be derived from partner definitions and the role played by the process in interactions with partners
BPEL 2.0
WSDL 1.1
BPEL-defined
WSDL extensions

23. Recursive Composition
BPEL processes interact with WSDL services exposed by business partners
Interfaces exposed
by the BPEL process
Interfaces consumed
by the BPEL process
WSDL
Loan Approval
PortType
Web
Service
Web
Service
Loan Approval Process
receive
Financial Institution‘s
Web Service
(Loan Approver)
invoke
reply

24. Composition of Web Services
Service A
Service P
Service B
receive
invoke
receive
invoke
invoke
A’s WSDL
P’s WSDL F
B’s WSDL
Partner Link Type
Partner Link Type

25. Peer-to-peer conversational partner relationship
Partner Links
process
partner
link
receive
Inbound request – service provided by the process
invoke
Outbound request – service required by the process
partner link type
Peer-to-peer conversational partner relationship
WSDL
port type
myRole
Provided port type
WSDL
port type
partnerRole
Required port type
Partner links are channels along which peer-to-peer conversations with partners take place

26. Variables 42 42 process WSDL message messages
Variables defined using WSDL messages
receive
request
invoke
request
response
reply
response 42
xsl:transform
assign
Variables are typed using WSDL messages or XML Schema elements or simple/complex types
Activities’ input and output kept in scoped variables
Assignment activities move data around 42
XML
schemas
XML Schema
elements / types
Variables defined using XML schema elements or types

27. ... Variable Properties process A property creates a name that has
semantic significance
beyond an XML schema type
getVariableProperty( variable, property )
Properties
isolate the process logic
from the details of a
variable definition 
XML schema element
WSDL message
part
...
property
alias
Typed properties are
mapped (aliased) to
parts of WSDL messages
or XML schema elements

28. Properties and Correlation Sets
receive
Submit purchase order
process instance 1
How to identify stateful instances
via stateless Web service interfaces?
purchaseOrder
cId = 0815
orderNo = 42
process
process instance 2
initiate
correlation set
customerId
orderNumber
customerId
orderNumber
Messages in
long-running conversations
are correlated to
the correct process instance
locate
process instance 3
process instance 3
receive
Query order status
queryOrderStatus
custId = 0815
oNo = 42 4
(0815, 49) 3
(0815, 42) 2
(0707, 11) 1
(0311, 33)
Typed properties defined in WSDL are named and mapped (aliased) to parts of several WSDL messages used by the process
process instance 4

29. Basic Activities process receive reply invoke Invoke a one-way or
request-response operation
Do a blocking wait for a
matching message to arrive / send a message in reply
exit
Immediately terminate execution of a business process instance
compensate
compensateScope
Invoke compensation on all completed child scopes in default order
Invoke compensation on one completed child scope
validate
assign
Update the values of variables or partner links with new data
Validate XML data stored in variables
wait
Wait for a given time period or until a certain time has passed
throw
rethrow
Generate a fault from inside the business process
Forward a fault from inside a fault handler
empty
No-op instruction for a business process
extensionActivity
Wrapper for language extensions

30. Structured Activities
process
flow
Contained activities are executed in parallel, partially ordered through control links
pick
Block and wait for a suitable message to arrive (or time out) B C A M1 M2 … A
sequence
Contained activities are performed sequentially in lexical order
forEach
Contained activity is performed sequentially or in parallel, controlled by a specified counter variable 2. N. 1. … 2. N. 1. …
while
Contained activity is repeated while a predicate holds
repeatUntil
Contained activity is repeated until a predicate holds
if-elseif-else
Select exactly one branch of activity from a set of choices c1 c2 c …
scope
Associate contained activity with its own local variables, partner links, etc.,
and handlers c

31. Nesting Structured Activities
sequence
<sequence>
<receive .../>
<flow>
<invoke .../>
<while ... >
<assign>...</assign>
</while>
</sequence>
<invoke ... />
</flow>
<reply .../>
receive
flow
sequence
sequence
invoke
receive
while
invoke
assign
reply

32. Scopes
Scopes provide a context which influences the execution behavior of its enclosed activities
process
scope
scope
Local declarations – partner links, message exchanges, variables, correlation sets
scope
Local handlers – event handlers, fault handlers, a termination handler, and a compensation handler
scope
Compensation handler to undo persisted effects of already completed activities
Termination handler to deal with forced scope termination (external faults)
primary activity
scope
Isolated scopes provide control of concurrent access to shared resources
scope
scope
scope
scope

33. 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
invoke
invoke
invoke
reply

34. Motivation OASIS and WS-BPEL Main Concepts Examples Status and support

35. Graph-Oriented Authoring Style
flow
riskAssessmentPT
loanApprovalPT
amount < 10000
amount >= 10000
receive
loan
assessor
loan
approver
invoke
risk = "high"
invoke
assign
risk = "low"
approved = "true"
reply
approved = "false"
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

36. Structured Authoring Style
sequence
flow
if-else
if buyer$$ < seller$$
else
receive
(buyer)
assign
"failure"
reply
(seller)
reply
(buyer)
receive
(seller)
assign
"success"

37. Parallel Processing flow parallel forEach scope scope event handler
. . .
scope
event
handler
event
handler
event
handler
event
handler
event
handler
event
handler
. . .
event
handler
. . .
event
handler
event
handler
event
handler
. . .
. . .
Use better example
. . .

38. Fault Handling & Compensation
Process
sequence
fault
handler
scope
scope
notify
manager
compensation
handler
fault
handler
compensate
charge
credit card
refund
customer
ship
goods
rethrow
Use better example

39. Dynamic Partner Link Assignment
Process A
Process B
assign
EPR
PortType-B
invoke
service
receive
request
Partner
Link Type
A-role
B-role
partner
link
assign
EPR
receive
response
invoke
callback
PortType-A

40. Abstract & Executable Processes
Contain the partner’s business logic behind an external protocol
Model actual behavior of a participant in a business interaction
Encompass enough detail to fully specify execution

41. 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

42. Executable Processes View
Travel Reservation - Example
Abstract Process View
Traveler Process
Agent Process
Airline Process
select
airline
reserve
seats
charge
credit card
plan
trip
get
itinerary
get
order
submit
to agent
order
tickets
receive
confirmation
Partner links are channels along which peer-to-peer conversations with partners take place
receive
tickets
receive
confirmation
confirm
flight
send
confirmation
send
tickets

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

44. Abstract Profiles & 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

45. Motivation OASIS and WS-BPEL Main Concepts Examples Status and support

46. 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

47. What’s 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

48. What’s new since BPEL 1.1? Variable initialization Partner links
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 bpel:doXslTransform(...)
XPath access to variable data
XPath variable syntax $variable[.part]/location
Flow activity
Scope isolation and link semantics

49. What’s new since BPEL 1.1? Fault handlers Compensation 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)
Opacity and omission of activities, expressions, attributes

50. 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
Twister (open source)

51. WS-BPEL Application Areas
Business Process Design
Autonomic Computing
Grid Computing
Semantic Web

52. 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

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

54. WS-BPEL Follow-on Work
BPEL4People
Human user interactions
BPEL Subprocesses
Based on a coordination protocol
BPELJ
Inline Java code in activities and expressions
Currency with related standards
WSDL 2.0, XPath 2.0, XQuery, etc.

55. WS-BPEL Resources WS-BPEL 2.0 – Committee Specfication (03/2007)
OASIS Technical Committee
Info aggregator sites
Wikipedia
BPEL Resource Guide
Numerous books and conference papers
Analyst reports
BPEL4WS 1.1