Dancing with Services

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Dancing with Services

• 10th January 2005
• Steve Ross-Talbot
• Pi4 Technologies

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Agenda

• Choreography
• WS-CDL
• Tools
• The future

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Choreography - the beginning

• Working Group formed January 2003
• Initially tasked with defining business processes
  (aka BPML and BPEL) in a Web Service context
• Focus became a behavioral contract language for
  distributed systems

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Choreography - milestones

• Requirements document published in
• Invited experts (Milner, Honda, Yoshida) joined
  in
• Published first draft of WS-CDL in
• Published last call draft of WS-CDL in
• Published candidate recommendation draft of
  WS-CDL in
• Published working draft of WS-CDL primer in

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Choreography - today

• Primer likely to be published as a working note
  end Q1 2006
• Formal underpinnings likely to be published as a
  working note Q22006
• Implementations ..
• Pi4 Technologies (www.pi4soa.org)
• Imperial College
• Trustcom
• One other
• Users .
• 3 vertical standards organisations
• 2 Banks
• 1 Telco

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WS-CDL

• An XML language for describing the behavioral
  contract of collections of peered services in
  order to achieve some goal
• Akin to UML sequence diagrams with no ambiguities
  and a robust behavioral type system

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WS-CDL - Structure
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WS-CDL - An example
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WS-CDL - An example
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WS-CDL - An example
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WS-CDL - An example
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WS-CDL - An example
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WS-CDL - Structural clarity
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WS-CDL - Structural clarity
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WS-CDL - Can I dance?
The dancers Are the services in an SOA The
dance steps Are the interactions
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WS-CDL - Can I dance?
Gateway svc asks Validation svc to validate trade
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WS-CDL - Can I dance?
Validation svc asks RefData svc to lookup various
components as part of validation
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WS-CDL - Can I dance?
Once validation is complete Validation svc
informs Gateway svc
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WS-CDL - Can I dance?
Gateway svc asks Transaction svc to persist the
validated trade
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WS-CDL - Can I dance?
Transaction svc stores trade in Repository
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WS-CDL - Can I dance?
Gateway svc asks Cashflow svc and Confirm svc to
execute in parallel
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WS-CDL - Can I dance?
Confirm svc communicates with various other svcs
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WS-CDL - Can I dance?
RefData svc could have returned a fault to the
Validation svc because a counterparty was invalid
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WS-CDL - Can I dance?
As a result of a fault the Validation svc sends
the Exception svc a message to alert someone of
the problem.
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WS-CDL - Can I dance?
Which may get fixed in-situ
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WS-CDL - Can I dance?
And so validation is repeated
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WS-CDL - Can I dance?
The Gateway svc is unaware that problems occurred
and were fixed.
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WS-CDL - Can I dance?
But the Exception svc might not be able to fix
the problem. It sends a fault back to the
Validation svc
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WS-CDL - Can I dance?
Which enables an exception block in which a
further message is sent from the Validation svc
to the Exception svc to inform someone of a major
problem.
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WS-CDL - Can I dance?
And the conversation over the services is
terminated
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WS-CDL - I cant dance because
Gateway
Validation
RefData
Exception
Validation succeeds
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WS-CDL - I cant dance because
Gateway
Validation
RefData
Exception
Validation succeeds after a fix
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WS-CDL - I cant dance because
Gateway
Validation
RefData
Exception
The dance steps are incomplete. There are too
many pages of instructions.
Validation fails terminating the conversation
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WS-CDL - I can dance
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WS-CDL - Tools

• Open Source www.pi4soa.org Eclipse plugins
• Validating editor (graphical and tree based)
• Behavioral Monitoring
• CDL2Java (1.4, 1.5), CDL2BPEL (1.X, 2.0) ,
  CDL2WSDL (1.1, 2.0), CDL2EPP
• Project members
• Steve Ross-Talbot, Gary Brown (lead), Nobuko
  Yoshida, Kohei Honda, Marco Carbone, Robin
  Milner, Charlton Barretto
• Custodian www.pi4tech.com
• A new way to engage with academia
• Royalty free
• IP free

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WS-CDL - Tools
Graphical Grammar
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WS-CDL - Tools
Graphical Grammar
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WS-CDL - Tools
Graphical Grammar
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WS-CDL - Tools
Graphical Grammar
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WS-CDL - Tools
Code Generation and Deployment
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WS-CDL - Tools
Behavioral Monitor
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WS-CDL - The future

• Round tripping (Java2CDL and CDL2Java)
• Liveness properties
• Bisimulation (for conformance)

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The End