Chapter 12: Coordination Frameworks for Web Services Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005

Chapter 122Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Highlights of this Chapter WSCL: Web Services Conversation Language WSCI: Web Service Choreography Interface WS-Coordination Web service transaction types BTP: Business Transaction Protocol

Chapter 123Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WSCL: Web Services Conversation Language Business Interchange Requirements The parties must agree on the documents to be exchanged, and the semantics of the documents (defined by XML, XML Schema, RDF, and OWL) The parties must agree on the protocol used to transmit a document, such as SOAP-RPC, asynchronous SOAP, or ebXML transport, routing, and packaging The parties must know each other’s location An ordering of the documents to be transmitted must be specified: a conversation

Chapter 124Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Parts of a WSCL Specification Document Type Definitions: specify what types of XML documents will be exchanged Interaction Types: Send, Receive, SendReceive, ReceiveSend, Empty <OutboundXMLDocument id="Invoice" hrefSchema=" <InboundXMLDocument id="Payment" hrefSchema=" Transitions: order of the interactions Conversation: a name for the conversation and a list of all interactions and transitions in it

Chapter 125Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Concepts in WSCL

Chapter 126Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Well-Formed Conversations All interactions are reachable from the initial interaction. The final interaction is reachable from all interactions If a transition from interaction A to interaction B specifies a SourceInteractionCondition, then all transitions from A to B do so The final interaction and transitions to the final interaction unambiguously clarify for each participant when a conversation is finished

Chapter 127Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Example Conversation Definition

Chapter 128Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Example WSCL Specification <InboundXMLDocument hrefSchema= id="LoginRQ"/> <OutboundXMLDocument hrefSchema= id="ValidLoginRS"/> <OutboundXMLDocument hrefSchema= id="InvalidLoginRS" /> …

Chapter 129Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Example WSCL Specification (cont.) …

Chapter 1210Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WSCL Limitations Conversation is limited to two participants – multi-party interactions not supported Excellent graph primitives but no support for iteration or recursion Conversations modeled as scripted procedures, but procedures are not flexible Cooperation not supported Exception handling is low level (syntactic)

Chapter 1211Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WSCI: Web Service Choreography Interface WSCI describes the flow of messages exchanged by a Web service that is interacting with other services according to a choreographed pattern WSCI is an enhancement to WSDL (inserted within a WSDL file)

Chapter 1212Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Example WSCI Add-In to WSDL File <action name="ReceiveLogin“ role="tns:StockQuoteWS“ operation="tns:QuoteToUser/LogIn"/> <action name="ReceiveStockQuoteRequest" role="tns:StockQuoteWS" operation="tns:QuoteToUser/ProvideQuote"> <action name="ReceiveLogout“ role="tns:StockQuoteWS“ operation="tns:QuoteToUser/LogOut"/> <action name="QueryNYSE" role="tns:StockQuoteWS“ operation="tns:QuoteToUser/QueryNYSE"/>

Chapter 1213Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Example WSCI for Transaction and Compensation <action name="NotifyUnavailable" role="NYSE“ operation="tns:NYSEtoBroker/NotifyUnavailable"/> <action name="BuyShare" role ="Broker" operation="tns:BrokerToNYSE/BuyShare"/> defs:fundsRemain <action name="BuyShare" role ="Broker" operation="tns:BrokerToNYSE/BuyShare">

Chapter 1214Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WS-Coordination WS-Coordination is the specification for a service whose job is to coordinate the activities of the Web services that are part of a business process A coordination service is an aggregation of three services: Registration – for parties to register with the coordinator Activation – to create an instance of a coordination context Coordination protocol – to define the specific protocol to be followed

Chapter 1215Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WS-Coordination Service

Chapter 1216Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WS-Coordination Service

Chapter 1217Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns WS-AtomicTransaction: Protocol for an Atomic Transaction The travel agency and the airline can perform 2PC, but the museum can perform only a simple, zero-phase update

Chapter 1218Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Business Transaction Protocol (BTP)

Chapter 1219Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns Chapter 12 Summary