WS Choreography v.0-1 Overview This is work-in-progress David Burdett, Commerce One 18 June 2003

Commerce One Copyright © Topics Feature Overview XML Structures Whats missing Issues

Feature Overview

Commerce One Copyright © Features Reusability A choreography definition is reusable in different contexts with different software and different message formats State Driven Processes or organizations that take part in choreographies maintain their state in the choreography Cooperative Organizations Describes how independent organizations or processes cooperate Verifiable Choreography definition can be used to verify that a Choreography is being followed correctly (How not yet defined) Multi-Party The specification allows Choreography Definitions with any number of organizations or processes involved Modular An "import" facility allows separately define components to be imported

Commerce One Copyright © Reusability Roles Describes the type of a process/organization behavior e.g. a Buyer or a Seller States Identifies the point within a choreography a Role has reached e.g. a Buyer State could be OrderSent after sending an Order Interactions Communicating information from one Role to another for a reason. e.g sending an Order to request a purchase of goods Message Families The set of messages that serve the same or similar purpose. e.g a RosettaNet Order, a UBL Order, an EDI Order, are all the same Processes Occurs as a result of some event such as a change of State

Commerce One Copyright © Why Reusability is important Big Co ($$$$$) Medium Co ($$$) Small Co ($) 1. Work my way or you dont get my business! 2. OK 3. Work Big Cos way or we cant do business! 4. STOP!!!! I cant afford to implement all these ways. Ill just continue with fax! 3a. Work Bigger Cos way or we cant do business! Medium Co 2 3b. Work even Bigger Cos way or we cant do business! Medium Co 3 3c. Work Mega Cos way or we cant do business! Medium Co 4 Developing reusable ways of doing business* that are based on common standards are a pre-requisite to bringing smaller businesses into widespread eCommerce 5. Big Co doesnt realize the benefits of automation as they cant extend all the way down the supply chain *Choreography definitions are just one of the essential parts!

Commerce One Copyright © Legend State Driven SellerBuyer Check Order Send Order Send Order Error Process Order Error New Order Created Order Error Message Checked Order Checked OK Order Checked Rejected Order Checked Error Order Sent Order Received Order Error Received Order Error Sent Interaction Process State

Commerce One Copyright © Interactions, Reliable Messaging and Signals SellerBuyer Check Order Send Order Order Sent Order Received Reliable Messaging Ack. Message Checked OK Message Processing Started Message Processing Complete Signals Reliable Messaging Interaction … the other messages are implementation dependent The Choreography definition defines just the messages that cause the state to change …

Commerce One Copyright © Cooperative Organizations SellerBuyer Check Order Send Order Send Order Error Process Order Error New Order Created Order Error Message Checked Order Checked OK Order Checked Rejected Order Checked Error Order Sent Order Received Order Error Received Order Error Sent xxx The Buyer cant control what the Seller does and vice versa … … but they both have to agree how they will cooperate … Private Process … which means they must have a shared understanding of what each will do!

Commerce One Copyright © Checking Choreography Progress SellerBuyer Send Order Order Sent Order Received ERP Record State Choreo- graphy Defin- ition State DB Shared Common Choreography Definition Check State State Errors Send Order Error Order Error Received Order Error Sent Record State Choreo- graphy Defin- ition Check State State DB ERP State Errors

Commerce One Copyright © Other Features Multi-Party Choreographies Any number of roles can take part One definition for all roles – makes sharing easier Importing Definitions Allows reusability of individual definitions, e.g. messages, roles, etc Extending Choreography Definitions Allows one Choreography to extend another … perhaps should be composition instead! Choreography Dependencies Once choreography can only execute after another, e.g. You can only query the state of a choreography if there is another choreography instance to query Semantic Definitions Two ways of defining semantics: in the XML, or at a URL Multi-lingual

XML Structures Note all attributes are required unless stated as optional

Commerce One Copyright © Choreography Definitions in multiple languages Import definitions from other files (works like WSDL) Define the roles involved Define the Message Families Define the Interactions Define one or more Choreography Definitions The same definitions can be reused in multiple choreographies

Commerce One Copyright © Choreography XML... Default language for content of Description elements

Commerce One Copyright © Description XML <Description language="en-uk" ref=" This section contains a set of choreographies for Order Management Optional. If present, over- rides default language for content Optional. If present is URL of more detailed readable specification Semantic definitions Description elements can always occur zero or more times. Each occurrence must be for a different language

Commerce One Copyright © Import XML <Import namespace=" location=" Import works in the same way as a WSDL Import

Commerce One Copyright © Role & State A Role may have one or more states

Commerce One Copyright © Role & State XML This role represents the seller of goods or services... A Role name must be unique within a choreography file State names must also be unique within a choreography file States can also have a Description (not shown)

Commerce One Copyright © Message Family Messages in this family contain information to convey a request to purchase goods or services Message Family name must be unique within a choreography file URN uniquely identifies the Message Family

Commerce One Copyright © Interaction Definitions Send the order From the Buyer to the Seller <InteractionEndStates fromState="OrderSent" toState="OrderReceived"/> The name of the Interaction Sending Role Receiving Role Whats being sent State of the sending role after the message is sent State of the receiving role after the message is received

Commerce One Copyright © SellerBuyer Interaction End States Check Order Send Order New Order Created Order Sent Order Received Sending Role Receiving Role From State To State

Commerce One Copyright © Choreography Definition Allows one Choreography Definition to be the extension of another Declares a Choreography can only be followed if another choreography has been followed first Identifies the states that indicate the start and end of a choreography Defines the usage of an interaction Defines a process Interactions and processes can occur in any order

Commerce One Copyright © Choreography Definition (XML) <ChoreographyDefinition name="OrderManagementChoreography1" urn=" A simple Order Management Choreography that includes the sending of an order from a Buyer to a Seller and the Seller returning an error if a problem is found Unique name Unique URN List of start and end states List of Interactions and Processes in any order

Commerce One Copyright © Start End States A state that indicates the start of the choreography A state that may be a last state for a Role in the choreography A state that is a last state for a Role in the choreography

Commerce One Copyright © Start End States example Start State Conditional End State SellerBuyer Check Order Send Order Send Order Error Process Order Error New Order Created Order Error Message Checked Order Checked OK Order Checked Rejected Order Checked Error Order Sent Order Received Order Error Received Order Error Sent End State If the Seller finds no problems with the Order, then OrderSent is the Buyers final state. But if problems are found then OrderErrorMessageChecked is the Buyers final state There is one Start state, but each Role must have one or more end states

Commerce One Copyright © Interactions and Processes A Boolean expression of states that must be true for the Interaction to occur A Boolean expression of states that must be true for the Process to occur A list of the possible end states for a process

Commerce One Copyright © Interaction and Process XML Send the order to the seller The seller checks the order. SellerBuyer Check Order Send Order New Order Created Order Checked OK Order Checked Rejected Order Checked Error Order Sent Order Received Reference to Interaction Definition Role that executes the process

Commerce One Copyright © Complete Choreography Example In this Choreography Definition, a Buyer sends an Order to a Seller. The Seller returns an Error Message, if the Order cannot be processed Send the order to the seller The seller checks the order. The order was in error - send an error Buyer Processes Order Error Message

Commerce One Copyright © Whats Missing from the spec Choreography Bindings to WSDL and SOAP Handling errors e.g. Message (document) errors, Process timeouts, transmission errors, etc Composing new choreographies out of existing choreographies Relationships to Reliable Messaging, signals and other protocols such as BTP and WS Transaction How Imports work Detailed schema validation rules, e.g. interdependencies Guidance on how to do run-time checks that a choreography is being correctly followed Inquiring on another roles choreography state Recovering from a failure of the choreography … this list is definitely not complete …

Commerce One Copyright © Issues Import Should also allow imports of process definitions Handling name conflicts between imports Roles & States name attributes are IDs, should probably make them unique just within their scope Roles should also be identified by a URI Processes Should be independently defined and importable