Peer-to-Peer Business Communities: Mapping Public Choreography Protocols to Individual Implementation Mechanisms

1
Peer-to-Peer Business CommunitiesMapping Public
Choreography Protocols to Individual
Implementation Mechanisms
Adomas Svirskas with Bob Roberts Michael
Wilson 28 February 2006, San Sebastian, Spain
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Agenda

• Target Web Based Communities
• Service Oriented Architecture
• Business Protocols and Service Choreography
• Mapping to the Implementation Mechanisms

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Target Web Based Communities

• Communities of peers, as opposed to the
  master-slave model
• Communities requiring rather formal rules for
  their interaction
• Business
• Government
• Public sector
• Mix of the above
• Communities of changing rules

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The Enabler - SOA

• Service Oriented Architecture
• Services represent what businesses do
• Services share only common message format, which
  allows them to be independent (loosely coupled)
  and reusable
• These services communicate according to the
  standards Web Services, WS-, WS-I, etc.
• Service Oriented Architecture (SOA) is maturing
• Business take-up is increasing
• Technical basis is strengthening

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SOA/WS standards (just a few)
Company Agreements, W3C OASIS W3C/OASIS W
3C IETF
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The need for business protocols

• Disparate services alone do not solve the problem
  they can cause chaos if used without an order
• In order to accomplish a common meaningful goal,
  the services should be used according to the
  business protocols
• The protocols represent the practical side of the
  business models
• They specify business message exchanges between
  the peers business partners

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Service Choreography 5

• Describes business protocols from the global
  point of view, i.e. commonly agreed rules come
  first
• It is a behavioral contract language for
  distributed systems of independent peers
• Is enacted individually by the peers, without any
  intermediary
• Is a declarative, non-procedural business
  collaboration backbone

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Svc. Choreography Initiatives

• Common protocol (agree on the protocol in advance
  then follow it) based
• ebXML Business Process Specification Schema
  (ebXML BPSS or ebBP)
• OASIS ebXML Business Process Technical Committee
• Web Services Choreography Description Language
  (WS-CDL)
• W3C Web Services Choreography Working Group
• Mediation (grow independently, resolve the
  protocol inconsistencies later) based
• WSMO choreography and orchestration model
• WS Modeling Ontology Working Group

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ebBP and WS-CDL

• Although WS-CDL and ebBP address similar problem
  domains, the divergent foci of the two enables
  them to be layerable
• The WS-CDL focuses primarily (not only) on the
  Web Service perspective, while the ebBP describes
  the pure business message flow and state
  alignment. As such they are not mutually
  exclusive
• The ebBP v2.0 (which is nearing a vote for OASIS
  Committee Draft) supports mapping of Business
  Transaction patterns to abstract operations
  through the OperationMapping constructs,
  definition of business QoS guidelines, and it can
  be supported by CPPA, which maps to concrete
  WSDL
• These mechanisms provide the avenue for WS-CDL
  and ebBP compatibility.

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Svc. Choreography - WS-CDL 2,5

• WS-CDL is an XML-based language that can be used
  to describe the common and collaborative
  observable behavior of multiple services that
  need to interact in order to achieve some goal
• Common collaborative observable behavior is the
  phrase used to indicate describe the behavior of
  a system of services, for example buyer and
  seller services, from a global perspective
• Such observable behavior is described as a set of
  functions, possibly with parameters, that a
  service offers coupled with error messages or
  codes that indicate failure along with the return
  types for the functions offered.

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Service Orchestration in SOA/WS

• Orchestration specifies the behaviour of a
  participant in a choreography by defining a set
  of "active" rules that are executed to infer what
  to do next
• Once the rule is computed, the orchestration
  runtime executes the corresponding activity(ies).
  
• Orchestration assumes existence of an entity,
  which is the central point of control (i.e. the
  conductor in an orchestra) and governs overall
  workflow of activities, effectively composing a
  new service from existing services

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Choreography vs Orchestration
Orchestration
From 1
Orchestration is akin to traffic lights where
events are controlled centrally, whereas
Choreography is more like a roundabout, where
each participant is following a prearranged set
of rules.
Paul Downey, http//blog.whatfettle.com/archives/0
00250.html
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Choreography along with Orchestration
Orchestration
Orchestration
From WS-CDL Specification 2
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Collaborative Business Processes
Collaboration Definition
Orchestration engine
Distribution
choreography
Deployment
CBP Choreography The business protocol defining
high-level interactions across administrative
domains
Generation/Adaptation of actual executable
processes and their views
From 4, (c) TrustCoM project
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Flexible Choreography support
"While business protocols are application
specific, much of the software required to
support such protocols can be implemented as
generic infrastructure components. For example,
the infrastructure can (1) maintain the state of
the conversation between a client and a service,
(2) associate messages to the appropriate
conversation, or (3) verify that a message
exchange occurs in accordance to the rules
defined by the protocols (for example WS-CDL) 3
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Virtualised Services
RBVO
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Gateway anatomy

• Patterns
• Acceptor-Connector
• Chain of Responsibility
• Handlers
• Application specific
• Application independent
• Rule-based mapping

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Related Work

• Pi4Tech (www.pi4tech.com) has launched an open
  source initiative Pi4SOA.org
• An interactive graphical WS-CDL editor (Eclipse
  plug-in)
• Validation of choreography descriptions
• Scenario testing
• Run-time monitoring
• End-point skeleton (Java, WSDL) generation and
  deployment (Axis)

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Conclusions

• Good business models come first
• Service Oriented approach allows flexible
  integration and single-platform approach
• Service choreography describes and helps to
  enforces the business protocols
• Intelligent support of choreography scripts by
  the peers is the key for adaptivity

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Thank you!

• Adomas Svirskas
• adomas_at_svirskas.com
• Researcher
• Vilnius University, Lithuania
• Kingston University London, UK

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References

• 2 Booth, D 2005, From Web Services to the
  Semantic Web Global Data Reuse. 2005.
  http//www.w3.org/2005/Talks/0110-dbooth-semweb
• 3 WS-CDL 2005, Web Services Choreography
  Description Language Version 1.0. W3C Candidate
  Recommendation, http//www.w3.org/TR/2005/CR-ws-cd
  l-10-20051109/
• 7 G. Alonso et al. Web Services Concepts,
  Architectures and Applications Springer Verlag
  2004 ISBN 3-540-44008-9
• 11 M.D. Wilson, The TrustCoM Framework. A
  TrustCoM (www.eu-trustcom.com) workshop at
  PRO-VE05, Valencia, Spain, 2005
• 12 S. Ross-Talbot, "Orchestration and
  Choreography Standards, Tools and Technologies
  for Distributed Workflows", NETTAB Workshop -
  Workflows management new abilities for the
  biological information overflow, Naples, Italy,
  2005