Web Services Choreography Description Language

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Web Services Choreography Description Language
W3C Choreography WG 21 Sept 2003
Jeff Mischkinsky jeff.mischkinsky_at_oracle.com Nick
olas Kavantzas nickolas.kavantzas_at_oracle.com Goran
Olsson goran.olsson_at_oracle.com
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Agenda

• Goal
• Web Services Platform
• Web Services Choreography Description Language

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Goal

• Specify a declarative language that describes
  collaborations of Web Services participants by
  defining their complementary observable behavior

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Current Web Services platform

• Core communication framework bridging
  heterogeneous computational models
• Loosely-coupled, stateless
• Exchange of type checking information

5
Emerging Web Services platform
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Emerging Web Services platform

• Reliable Messaging layer
• Guaranteed delivery
• Message ordering
• Exactly once
• Context, Coordination, Transaction layer
• Bridge heterogeneous coordination protocols
• Business Process Language layer
• Implements Web Services based applications
• Models non-observable (internal) behavior
• BPEL, BPML, XPDL
• Define control flows
• Manage private data

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WS-CDL Design Goals

• Model the complementary observable behavior of
  Web Services participating in a common business
  transaction
• Based on a formal model
• pi-calculus variation

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WS-CDL Concepts

• Web Services participants interact and align
  their shared information
• Synchronized document exchanges
• Progress is guarded by commonly defined ordering
  rules
• Interactions with common behavioral
  characteristics are combined to form a behavioral
  unit
• Enables re-usability in different business
  contexts

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WS-CDL Concepts

• Information Typing
• Identifying Coupling of WS participants
• Information driven collaboration
• State
• Activities
• Reaction
• Choreography
• Packaging

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Information Typing

• Document type
• Aliases WSDL message type, XSD type, XSD element
• Supports future type systems
• Token type
• Specify name and type of piece of information
• Uses WS-CDL Document type of the attribute
• Token Locater type
• Specify rules for selecting a piece of
  information
• WS-CDL Document type
• WSDL message part
• XPATH query of document

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Static coupling Roles Relationships

• Role type
• Specify the observable behavior, in terms of the
  operations, a WS participant can perform
• One or more WSDL interface type(s) named as
  behavior type
• Relationship type
• Specify the mutual commitments, in terms of the
  Roles, two WS participants are required to
  provide
• Two WSDL interface types

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Dynamic coupling Channel

• Identify a contact-point, through which two WS
  participants interact
• A contact-point describes
• the service type of a participant, using Token
  type(s) within a reference marker
• the business process type implementing a WS
  participant, using Token type(s) within an
  identity marker
• Identify a conversation between two or more WS
  participants
• A conversation groups a set of related document
  exchanges, using Token type(s) within an identity
  marker

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State

• Capture information shared between WS
  participants
• Affect the progress of their common business
  transaction
• State definitions
• Define Documents
• Typed with a documentType
• Define Channels
• Typed with a channel type
• Specify the Role of the WS participant the state
  resides in

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Activities Interact

• Enable WS participants to communicate and align
  their shared state
• Synchronized document exchange between two roles
  within a relationship
• Atomic, request accept of an operation through
  a channel
• WSDL One way or request-response
• Information flow
• request direction fromRole towards toRole
• response direction toRole towards fromRole

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Activities Interact (2)

• Align state that resides in one role with state
  that resides in the other role
• The aligned states are made available at the two
  roles

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Activities

• Declare
• Create and make available new state at a Role
• Repeat
• Sleep
• Inact
• Compensate

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Reaction

• Guard a set of activities
• Express interest on the availability of zero, one
  or more state information
• When the state is/become available and a guard
  condition evaluates to true, the enclosed
  activities are enabled
• In parallel or sequentially
• Repeat marks the re-enablement of a reaction
• reaction group marks the mutual-exclusive
  enablement of a set of activities

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Choreography

• Interactions with common behavioral
  characteristics are combined to form a behavioral
  unit
• Enumerate all the binary relationships
  interactions act in
• Localize the visibility of state
• Using state definitions
• Prescribe alternative patterns of behavior
• Using reactions
• Enable Recovery
• Backward handle exceptional conditions
• Forward compensate already completed activities
• Recursively combine Choreographies to form new
  Choreographies

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Packaging

• Aggregate Import
• Document types, toke types, toke locator types,
  role types, relationship types, channel types
• One or more choreographies
• Import XSD, WSDL types

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WS-CDL Example

• The example is a multi-participant choreography
• Illustrates a simple purchase sequence
• It involves four participants, Roles
• Buyer, Seller, Credit Checking Service, and
  Inventory Service
• Main choreography involves 3 relationships
• Buyer-Seller
• Seller-Credit Checking Service
• Seller-Inventory Service

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WS-CDL Example cont.

• The Buyer initiates an interact and the
  Choreography 
• With the Seller to align the Purchase Order
• The Seller, when the Purchase Order is available,
  initiates 3 interactions
• With the Buyer to acknowledge receipt of the
  Purchase Order
• With the Credit Checking Service to check Buyers
  credit
• With the Inventory Service for product
  availability

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WS-CDL Example cont.

• The Seller reaction is guarded by the response
  interactions from Credit Checking Service and
  Inventory Service
• If both interactions result are positive, the
  order is processed and the Purchase Order
  Response is sent
• If either interaction indicate a negative result
  a Purchase Order Reject message is sent to the
  Buyer

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WS-CDL Example cont.
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WS-CDL Example cont.

• Buyer interacts with Seller to create a Purchase
  Order
• Seller acknowledges the Purchase Order in an
  interact
• Seller interacts with Credit Service and
  Inventory service
• Credit and Inv. Services interacts with Seller
  with results
• Seller interacts with Buyer creating PO Response

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WS-CDL Example cont.Some Basic Constructs

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WS-CDL Example cont.Documents

• ltdocumentType name"purchaseOrderDocType"
• messageType"ponspurchaseOrderMsg"/gt
• ltdocumentType name"purchaseOrderAckDocType
• messageType"ponspurchaseOrderAckMsg"/
  gt
• ltdocumentType name"purchaseOrderRejectDocType"
• messageType"ponspurchaseOrderRejectMs
  g"/gt
• ltdocumentType name"purchaseOrderResponseDocType
  
• messageType"ponspurchaseOrderResponse
  Msg"/gt
• ltdocumentType name"creditCheckRequestDocType"
• messageType"ponscreditCheckRequestMsg
  "/gt

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WS-CDL Example cont.Tokens

• lttokenType namewarehouseRef" type"xsdanyUri"/gt
  
• lttokenType name"purchaseOrderID"
  type"xsdint"/gt
• lttokenLocator tokenName"snspurchaseOrderID"
• documentType "purchaseOrderDocType"
• part"PO"
• query"/PO/Order"/gt

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WS-CDL Example cont.roleType

• ltroleType name"Seller"gt
• ltbehaviorType name"sellerForBuyer"
• interfaceType"snsSellerPOP
  T"/gt
• ltbehaviorType name"sellerForCredit"
• interfaceType"snsSellerCre
  ditPT"/gt
• ltbehaviorType name"sellerForInventory"
• interfaceType"snsSellerInv
  entoryPT"/gt
• lt/roleTypegt

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WS-CDL Example cont.Relationships

• ltrelationshipType name"BuyerSellerBinding"gt
• ltrole type"Buyer"/gt
• ltrole type"Seller"/gt
• lt/relationshipTypegt

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WS-CDL Example cont.Channels

• ltchannelType name"purchaseOrderCHT"gt
• ltchannelDefinitionsgt
• ltchannel typepurchaseOrderResponseCHT
  
• directionrespondgt
  
• lt/channelDefinitionsgt
• ltrole type"Seller"/gt
• ltreferencegt
• lttoken name"warehouseRef"/gt
• lt/referencegt
• ltidentitygt
• lttoken name"purchaseOrderID"/gt
• lt/identitygt
• lt/channelTypegt

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WS-CDL Example cont.State Definitions

• ltstateDefinitions name"purchaseOrderChoreography
  State"gt
• ltstateType name"purchaseOrderAckDoc"
• documentType"purchaseOrderAckDocType"/gt
• ltstateType name"purchaseOrderDocAtBuyer"
• documentType"purchaseOrderDocType"
• roleType"Buyer"/gt
• lt/stateDefinitionsgt

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WS-CDL Example cont.Interacts

• ltinteract name"inventoryCheck"
• onChannel"inventory-channel"
• operation"inventoryCredit"
• initiateChoreography"true"gt
• ltparticipate
• relationship"SellerInventoryBindin
  g"
• fromRole"Seller"
• toRole"Inventory"/gt
• ltalign state"inventoryRequestDoc"
• with-state"inventoryRequestDoc"/
  gt
• lt/interactgt

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WS-CDL Example cont.Reactions

• ltreact name"creditApprovalInventoryApproval"
• group"ApproveOrReject
• relationshipTypeBuyerSellerBinding
• guard
• "cdlgetState(CreditCheckResponseDocAtSeller,
  
• \/Customer/Credit\)text() 'success'
  
• cdlgetState(InventoryResponseDocAtSeller,
• \/Order/Inventory\)text()'available'"gt
• ltinteract name"createOrderResponse
• lt/interactgt
• lt/reactgt

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WS-CDL Example cont.Choreography

• ltchoreography name"inventoryCheckChoreography"gt
• ltrelationship type"SellerInventoryBinding"/gt
• ltstateDefinitions
• nameinventoryCheckChoreographyStategt
• ltstateType name"inventoryCheckRequestDoc
• documentType"inventoryCheckRequestDocType"
  /gt
• ltstateType name
• "inventoryCheckResponseDocAtInventory
• documentType"inventoryCheckResponseDocType
  "
• roleType"Inventory"/gt
• ltstateType name"seller-channel-for-inventory
  
• channelType"inventoryCheckResponseCHT"/gt
• lt/stateDefinitionsgt
•  

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WS-CDL Example cont.Choreography

• ltreact name"purcaseDocAvailibility
• relationshipTypeSellerInventoryBinding
• sequentialtrue
• guard"purchaseOrderDocAtSeller"gt
• ltinteract name"inventoryCheck
• onChannel"inventory-channel
• operation"inventoryCredit"
• initiateChoreography"true"gt
• ltparticipate
• relationship"SellerInventoryBind
  ing
• fromRole"Seller
  toRole"Inventory"/gt
• ltalign state"inventoryRequestDoc"
• with-state"inventoryRequestDoc"/
  gt
• ltalign state"seller-channel-for-inventor
  y"
• with-state"seller-channel-for-inventor
  y"/gt
• lt/interactgt
•   lt/reactgt

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WS-CDL Example cont.Choreography

• ltrecover name"ncname"gt
• ltexception name"ncname"gt
• ChoreographyNotation
• lt/exceptiongt?
• ltcompensation name"ncname"gt
• ChoreographyNotation
• lt/compensationgt?
• lt/recovergt?
• lt/choreographygt

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WS-CDL Example cont.

• ltchoreography name"purchaseOrderChoreograpy"
  root"true"gt
•   ltchoreography name"buyerSellerChoreograp
  hygt
• ltinteract name"createOrderInteract/gt
• ltinteract name"createOrderAckInteract/gt
• ltchoreography name"sellerResponseChoreogra
  phy"gt
• ltinteract name"createOrderResponse/gt
• lt/choreographygt
• ltchoreography name"sellerRejectChor
  eography"gt
• ltinteract name"createOrderReject/gt
• lt/choreographygt
• lt/choreographygt
•   ltchoreography namecreditCheckChoreograp
  hygt
• ltinteract name"creditCheck/gt
• ltinteract name"creditCheckResponse
  /gt
• lt/choreographygt
•   ltchoreography name"inventoryCheckChoreog
  raphy"gt
• ltinteract name"inventoryCheck/gt
   
• ltinteract name"inventoryResponse
  /gt
• lt/choreographygt

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WS-CDL Example cont.

• ltchoreography name"purchaseOrderChoreograpy"
  root"true"gt
•   ltchoreography name"buyerSellerChoreography
  gt
• ltinteract name"createOrderInteract/gt
   
• ltinteract name"createOrderAckInteract/gt
• ltchoreography name"sellerResponseChoreogra
  phy"gt
• ltinteract name"createOrderResponse/gt
• lt/choreographygt
• ltchoreography
  name"sellerRejectChoreography"gt
• ltinteract name"createOrderReject/gt
• lt/choreographygt
• lt/choreographygt
•   ltchoreography namecreditCheckChoreogra
  phygt
• ltinteract name"creditCheck/gt
• ltinteract name"creditCheckResponse/gt
  
• lt/choreographygt
•   ltchoreography name"inventoryCheckChore
  ography"gt
• ltinteract name"inventoryCheck/
  gt  

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WS-CDL Example cont.

• ltchoreography name"creditCheckChoreography"gt
• ltrelationship type"SellerCreditBinding"/gt
• ltstateDefinitions namecreditCheckChoreographySt
  ategt
• ltstateType name"creditCheckRequestDoc
  documentType"creditCheckRequestDocType"/gt
• ltstateType name"creditCheckResponseDocAtCred
  it documentType"creditCheckResponseDocType
  roleType"Credit"/gt
• ltstateType name"seller-channel-for-credit
  channelType"tnscreditCheckResponseCHT"/gt
• lt/stateDefinitionsgt

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WS-CDL Example cont.

• ltreact name"purcaseDocAvailibility
• relationshipTypeSellerCreditBinding
• sequentialtrue guard"purchaseOrderDocAt
  Seller"gt
•  
• ltinteract name"creditCheck
  onChannel"credit-channel
• operation"checkCredit
• initiateChoreography"true"gt
• ltparticipate relationship"SellerCre
  ditBinding
• fromRole"Seller
  toRole"Credit"/gt
• ltalign state"creditCheckRequestDoc"
  
• with-state"creditCheckReques
  tDoc"/gt
• ltalign state"seller-channel-for-cre
  dit"
• with-state"seller-channel-fo
  r-credit"/gt
• lt/interactgt
•  

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WS-CDL Example cont.

• ltinteract name"creditCheckResponse
• onChannel"seller-channel-for-credit
• operation"creditResponse"gt
• ltparticipate relationship"SellerCreditBinding
  
• fromRole"Credit
  toRole"Seller"/gt
• ltalign state"creditCheckResponseDocAtCredit"
• with-state" creditCheckResponseDocAtSel
  ler"/gt
• lt/interactgt
• lt/reactgt
• lt/choreographygt

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WS-CDL

• Questions???
• Comments!!!