Jeff Mischkinsky Nickolas Kavantzas Goran Olsson Web Services Choreography Description Language W3C Choreography WG 21 Sept 2003

2 Agenda Goal Web Services Platform Web Services Choreography Description Language

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

4 Current Web Services platform Core communication framework bridging heterogeneous computational models – Loosely-coupled, stateless – Exchange of type checking information Transport Messaging Description Discovery HTTP, BEEP,IIOP, JMS, SMTP XML,Encoding SOAP WSDL UDDI

5 Emerging Web Services platformTransport Messaging Description Discovery HTTP, BEEP,IIOP, JMS, SMTP XML,Encoding SOAP WSDL UDDI Integration Business Process Languages: BPEL, XPDL, BPML Business Collaboration Language: Web Services Choreography Description Language Quality of Service Reliable Messaging SecurityTransaction Coordination

6 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

7 Model the complementary observable behavior of Web Services participating in a common business transaction Based on a formal model – pi-calculus variation WS-CDL Design Goals

8 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

9 WS-CDL Concepts Information Typing Identifying & Coupling of WS participants Information driven collaboration – State – Activities – Reaction – Choreography – Packaging

10 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

11 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

12 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

13 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

14 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

15 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

16 Activities Declare –Create and make available new state at a Role Repeat Sleep Inact Compensate

17 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

18 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

19 Packaging Aggregate & Import – Document types, toke types, toke locator types, role types, relationship types, channel types – One or more choreographies Import XSD, WSDL types

20 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

21 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

22 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

23 WS-CDL Example cont.

24 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

25 WS-CDL Example cont. Some Basic Constructs

26 WS-CDL Example cont. Documents <documentType name="purchaseOrderDocType" messageType="pons:purchaseOrderMsg"/> <documentType name="purchaseOrderAckDocType messageType="pons:purchaseOrderAckMsg"/> <documentType name="purchaseOrderRejectDocType" messageType="pons:purchaseOrderRejectMsg"/> <documentType name="purchaseOrderResponseDocType messageType="pons:purchaseOrderResponseMsg"/> <documentType name="creditCheckRequestDocType" messageType="pons:creditCheckRequestMsg"/>

27 WS-CDL Example cont. Tokens <tokenLocator tokenName="sns:purchaseOrderID" documentType ="purchaseOrderDocType" part="PO" query="/PO/Order"/>

28 WS-CDL Example cont. roleType <behaviorType name="sellerForBuyer" interfaceType="sns:SellerPOPT"/> <behaviorType name="sellerForCredit" interfaceType="sns:SellerCreditPT"/> <behaviorType name="sellerForInventory" interfaceType="sns:SellerInventoryPT"/>

29 WS-CDL Example cont. Relationships

30 WS-CDL Example cont. Channels <channel type= purchaseOrderResponseCHT direction= respond >

31 WS-CDL Example cont. State Definitions <stateType name="purchaseOrderAckDoc" documentType="purchaseOrderAckDocType"/> <stateType name="purchaseOrderDocAtBuyer" documentType="purchaseOrderDocType" roleType="Buyer"/>

32 WS-CDL Example cont. Interacts <interact name="inventoryCheck" onChannel="inventory-channel" operation="inventoryCredit" initiateChoreography="true"> <participate relationship="SellerInventoryBinding" fromRole="Seller" toRole="Inventory"/> <align state="inventoryRequestDoc" with-state="inventoryRequestDoc"/>

33 WS-CDL Example cont. Reactions <react name="creditApprovalInventoryApproval" group="ApproveOrReject relationshipType=BuyerSellerBinding guard= "cdl:getState(CreditCheckResponseDocAtSeller, \/Customer/Credit\)[text() = 'success'] && cdl:getState(InventoryResponseDocAtSeller, \/Order/Inventory\)[text()='available']"> <interact name="createOrderResponse ………

34 WS-CDL Example cont. Choreography <stateDefinitions name=inventoryCheckChoreographyState> <stateType name="inventoryCheckRequestDoc documentType="inventoryCheckRequestDocType"/> <stateType name= "inventoryCheckResponseDocAtInventory documentType="inventoryCheckResponseDocType" roleType="Inventory"/> <stateType name="seller-channel-for-inventory channelType="inventoryCheckResponseCHT"/>

35 WS-CDL Example cont. Choreography <react name="purcaseDocAvailibility relationshipType=SellerInventoryBinding sequential=true guard="purchaseOrderDocAtSeller"> <interact name="inventoryCheck onChannel="inventory-channel operation="inventoryCredit" initiateChoreography="true"> <participate relationship="SellerInventoryBinding fromRole="Seller toRole="Inventory"/> <align state="inventoryRequestDoc" with-state="inventoryRequestDoc"/> <align state="seller-channel-for-inventory" with-state="seller-channel-for-inventory"/>

36 WS-CDL Example cont. Choreography ChoreographyNotation ? ChoreographyNotation ?

37 WS-CDL Example cont.

38 WS-CDL Example cont.

39 WS-CDL Example cont.

40 WS-CDL Example cont. <react name="purcaseDocAvailibility relationshipType=SellerCreditBinding sequential=true guard="purchaseOrderDocAtSeller"> <interact name="creditCheck onChannel="credit-channel operation="checkCredit initiateChoreography="true"> <participate relationship="SellerCreditBinding fromRole="Seller toRole="Credit"/> <align state="creditCheckRequestDoc" with-state="creditCheckRequestDoc"/> <align state="seller-channel-for-credit" with-state="seller-channel-for-credit"/>

41 WS-CDL Example cont. <interact name="creditCheckResponse onChannel="seller-channel-for-credit operation="creditResponse"> <participate relationship="SellerCreditBinding fromRole="Credit toRole="Seller"/> <align state="creditCheckResponseDocAtCredit" with-state=" creditCheckResponseDocAtSeller"/>

42 WS-CDL Questions??? Comments!!!