SCA and WS-BPEL Martin Chapman Oracle

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SCA and WS-BPELMartin ChapmanOracle
www.oasis-open.org
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www.oasis-open.org

• What is SCA
• What is WS-BPEL
• How SCA and WS-BPEL fit
• SCA WS-BPEL Spec

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What is SCA?

• Service Component Architecture
• Developed by Open SOA Consortium
• Plug and Play Components
• XML definitions of components and assemblies
• Multiple implementation languages
• Recursive assembly of components
• Deployment of assemblies

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SCA Core Concepts

• Assembly Model
• how to define structure of composite
  applications
• Client Implementation specifications
• how to write business services in particular
  languages
• Java, C, BPEL, PHP.
• Binding specifications
• how to use access methods
• Web services, JMS, RMI-IIOP, REST
• Policy Framework
• how to add infrastructure services to solutions
• Security, Transactions, Reliable messaging

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SCA Core Concepts
Reference
Service
-
Java interface
-
Java interface
-
WSDL
PortType
-
WSDL
PortType
Properties
Composite
Property
setting
Component
Component
B
Service
Reference
A
Wire
Wire
Wire
Binding
Binding
Policies
Web Service
Web Service
SCA
SCA
JCA
JCA
JMS
JMS
SLSB
SLSB

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SCA What is it NOT

• Does not model individual workflows or ordering
  of service invocations
• use BPEL or other workflow languages
• Is not Web services
• SCA can use / may use Web services, but can also
  build solutions with no Web services content
• Is not tied to a specific runtime environment
• distributed, heterogeneous, large, small
• Does not force use of specific programming
  languages and technologies
• aims to encompass many languages, technologies

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What is WS-BPEL

• An orchestration language for Business processes
• Interaction with Partners via WSDL
• Process Control Flow
• Ordering of service invocations
• An OASIS Standard

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WS-BPEL What it is not

• An end-to-end language
• Does not explicitly describe flows thru multiple
  business processes
• Only shows directly connected partners
• Process a invokes b, b invokes ca does not know
  c
• A deployment or configuration language
• Vendor tooling needs to provide this
• Policy language needed

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SCA WS-BPEL Goals

• Bottom Up
• Allow existing BPEL processes to be used without
  change
• WS-BPEL and BPEL4WS 1.1
• Top Down
• Design SCA components then use WS-BPEL to
  implement
• May include SCA extensions to WS-BPEL for SCA
  property handling, and multi-destination Partners

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SCA WS-BPEL
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Friction Point

• WS-BPEL partnerLinks are client/server biased
• myRole and partnerRole
• No notion of who is client or server. A typical
  WS-BPEL process acts in both roles
• SCA Services and References are client/server
  based
• A client/server distinction based on who sends
  first message
• After first message, callbacks and converstions
  may proceed

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WS-BPEL partnerLinks
Partner Link Type
myRole
partnerRole

• WS-BPEL Process

External Service Java, c, BPEL
WSDL Port Type 1
WSDL Port Type 2
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SCA Services and References
WSDL Port Type 2
Component
Component
Reference
Service
A
Callback
WSDL Port Type 1
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Decide who is the Client

• To ensure SCA wires correctly
• Given a WS-BPEL defintion
• If a receive, pick, onEvent, is the first use of
  a partnerLink then
• myRole is an SCA Service
• Else
• myRole is a reference/callback

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SCA WS-BPEL Spec

• Rules for mapping partnerLinks to SCA Services
  and References
• Previous slide is a simplification
• Multiplicities need to be considered (0..1, 1..1,
  0..n)
• Naming services and references
• Reuse partnerLink names
• Scoped partnerLinks must be disambiguated

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SCA WS-BPEL Spec

• Support for SCA conversations
• Not to be confused with WS-BPEL correlation
  mechanism
• WS-BPEL specifications that use a partnerLink
  after a conversation has ended may be rejected
• An SCA generated conversation violation fault may
  be generated

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SCA WS-BPEL Spec

• SCA Extentions to WS-BPEL
• Only in SCA aware WS-BPEL definitions
• SCA Properties
• A ws-bpel variable can be defined as as SCA
  property and can be initialised by SCA
• Multi-valued References
• Ws-bpel partnerLinks are 0..1
• Sca extension to allow 0..m
• Multiple partners under the cover
• E.g. RFQ scenario

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SCA WS-BPEL Spec

• Only covers Executable WS-BPEL
• Abstract WS-BPEL cannot be an implementation
  language by definition

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Summary

• Tying the Nots!
• A workflow language (WS-BPEL)
• Process logic and service invocation ordering
• A standard deployment and configuration language
  (SCA)
• Dependencies between components
• Policy framework (SCA)
• An end-to-end view (SCA and BPEL)
• The two together is a happy partnership

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Acknowledgements

• The SCA BPEL Working Group
• Martin Chapman Oracle
• Sabin Ielceanu TIBCO Software, Inc
• Dieter Koenig IBM Corporation
• Michael Rowley BEA Systems, Inc.
• Ivana Trickovic SAP AG
• Alex Yiu Oracle

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Further Reading

• http//www.osoa.org
• SCA WS-BPEL Specification
• http//www.osoa.org/download/attachments/35/SCA_Cl
  ientAndImplementationModelforBPEL_V100.pdf?version
  1
• SCA WS-BPEL White Paper
• http//www.osoa.org/display/Main/SCABPELWhitePa
  per
• Relationship Between SCA and BPEL White Paper
• http//www.osoa.org/display/Main/Relationshipbetw
  eenSCAandBPEL