Building distributed systems using WS-CDL

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Building distributed systems using WS-CDL

• 10th June 2007
• Steve Ross-Talbot
• Chair Pi4 Technologies Foundation
• CTO Hattrick Software Ltd
• Chair W3C Web Services Choreography WG
• Thanks to
• Pi4 Technologies Foundation Ltd
  (www.pi4tech.com)
• Hattrick Software Ltd (www.hattricksoftware.com)
  
• World Wide Web Consortium (Choreography Working
  Group)

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Agenda

• Background
• p4 Technologies Foundation
• Hattrick Software Ltd
• WS-CDL
• Simple example
• Case study
• Research

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Background
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p4 Technologies Foundation

• Founded in November 2005
• Kohei Honda, Nobuko Yoshida, Marco Carbone, Robin
  Milner, Steve Ross-Talbot, Gary Brown
• Enable collaborative research between industry
  and academia in applying formalisms to
  distributed systems development

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p4 Technologies Foundation

• Bi-directional (open format for collaboration)
• Real world examples -gt academia
• Academia research -gt industry
• Forums for discussion
• www.pi4tech.org
• Open source environment for research and
  development. (Apache 2.0)
• CDL toolsuite
• Advanced type system

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p4 Technologies Foundation

• Results so far
• CDL tool suite - eclipse-based community edition
• Modeling editor
• Generation to wsdl, java, ws-bpel
• Export to html, bpmn, ws-cdl, uml
• Scenarios
• Editor
• Validation
• Vertical standards use (FpML, TWIST, ISO WG4)
• Modeling editor with wsdl, html, bpmn, ws-cdl and
  uml
• Scenrios editor and validation
• Complements existing vertical standards packs
• Static
• Document, Validated example message, XMLSchema,
  Example scenarios
• Dynamic
• Document, Validated example scenarios, WS-CDL
  description

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p4 Technologies Foundation
An example in CDM
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p4 Technologies Foundation
Exported to BPMN
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p4 Technologies Foundation
Exported to HTML
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p4 Technologies Foundation
Exported to HTML
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p4 Technologies Foundation
Exported to CDL
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p4 Technologies Foundation
Exported to CDL
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p4 Technologies Foundation
Support for scenarios validated against the
choreography
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Hattrick Software Ltd

• Commercial entity charged with solving the
  problems of automation of OTC Derivatives
  Trading.
• Long lived, complex peered processes in which
  parties may change roles
• ClearGate generic WS-CDL-based protocol
  enforcer/monitor

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WS-CDL
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WS-CDL

• A language to describe the collaborative
  external observable behavior of a set of peered
  systems/services/applications as an ordered set
  of interactions over one or more logical channels
  that connect them.

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Simple example
x
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Simple example
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Roles
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Relationships and Participants
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Channels and Info types
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Bindings
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Variables
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Interactions
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Choice
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Workunits
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Workunits
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Workunits
This is what we used
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Workunits
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Theory

• Global Calculus
• Distillation of WS-CDL
• Reduction rules, etc
• End point Calculus
• Correspondance to Global Calculus
• Reduction riles, etc

http//www.w3.org/2002/ws/chor/edcopies/theory/not
e.pdf
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Theory
http//www.w3.org/2002/ws/chor/edcopies/theory/not
e.pdf
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Theory
http//www.w3.org/2002/ws/chor/edcopies/theory/not
e.pdf
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WS-CDL Benefits

• A complete and unambiguous description of a
  distributed system of how peered roles or
  participants should interact and the order in
  which these interactions should take place.
• Enables code generation for a distrbuted system
  (end point projections) and guarantees
  interoperability of that system by design.
• Enables us to ask questions of a system so
  described
• Is it free from deadlocks, livelocks and races?

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Case Study

• FpML
• Financial Products Markup Language
• Policed by ISDA
• FpML today is
• A set of documents that describe the structure of
  how to encode financial products in XML
• XMLSchema to enable validation of correct message
  formats and a set of example messages
• There are a set of sequence diagrams to govern
  when to send what to whom

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Why WS-CDL?

• Consider the following
• Three companies wish to embark on a common
  business process. They are PartyA, PartyB and
  Confirmer.
• PartyA Is a seller selling some commodity
• PartyB Is a buyer buying some commodity
• Confirmer Acts as a central/brokered matching
  service that both PartyA and PartyB use to ensure
  that the contract between them matches (is
  valid). Confirming is legally binding.

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Why WS-CDL?

• This is a distributed system in which no one
  company has dominion over any other.
• PartyA, PartyB and Confirmer are all peers.
• PartyA, PartyB and Confirmer could be different
  parts of the same company or different companies.
• PartyA, PartyB and Confirmer need to interact to
  progress some common goal such as buying and
  selling some goods.

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Why WS-CDL?
Confirmer
PartyA
PartyB
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Why WS-CDL?

• How we do this today using older technology
• XMLSchema, UML Activity Models, Sequence
  Diagrams, etc
• How we do this with WS-CDL
• XML Schema, WS-CDL description,
  Scenarios/Sequence Diagrams, multiple formats for
  review

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Today
XMLSchema for data formats
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Today
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Today
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Today
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Today
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Using WS-CDL
Choreography description Parallel // PartyA
thread RequestTradeConfirmation
PartyA2Confirmer RequestTradeMatch
Confirmer2Matcher // PartyA thread //
PartyB thread RequestTradeConfirmation
PartyB2Confirmer RequestTradeMatch
Confirmer2Matcher .
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Using WS-CDL
While (not inConfirm) Choice // ----
Modification by PartyA ModifyTradeConfirmation
PartyA2Confirmer ModifyTradeMatch
Confirmer2Matcher // ---- Modification
by PartyB ModifyTradeConfirmation
PartyB2Confirmer ModifyTradeMatch
Confirmer2Matcher
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Using WS-CDL
Choice Sequence // ---- Confirmation
process Choice Sequence // ----
TradeMatched ---- TradeMatched
Matcher2Confirmer Parallel
TradeMatched Confirmer2PartyA
TradeMatched Confirmer2PartyB
ConfirmTrade PartyA2Confirmer Pa
rallel TradeConfirmed Confirmer2PartyA
TradeConfirmed Confirmer2PartyA
.. // End
Choice // End Sequence
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Using WS-CDL
Choice // ---- TradeMismatched
---- TradeMismatched Matcher2Confirmer Par
allel TradeMismatched Confirmer2Alleger
TradeMismatched Confirmer2Acceptor
// Alleger cancels CancelTradeCo
nfirmation Alleger2Confirmer CancelTradeMatch
Confirmer2Matcher Parallel
ConfirmationCancelled Confirmer2Alleger
ConfirmationCancelled Confirmer2Acceptor
.. // same but other way around // End
Choice
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Using WS-CDL
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Question
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Question
Is this valid against our model?
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Question
Session Joining?
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Completeness

• Sequence diagrams do not capture everything.
• WS-CDL does. It is unambiguous and precise.

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Research
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Future Directions

• WS-CDL 2
• Added participant instances, notifications,
  semantic annotations
• Type system implementation
• Carbone et al
• Scribble - language for multicore, multi-process
  communication-based programming
• Honda et al
• Two research project proposals
• COWS Contract Oriented Web Services
• ModelWeb Model-Driven Engineering of Policy- and
  Choreography- Based Web Services

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Questions