1. 19/05/2004 1 Web Services Composite Application Framework (WS-CAF) Presenter: Livia Predoiu, 19 May 2004 http://developers.sun.com/techtopics/webservices/wscaf/ Version 1.0 - 28 July 2003

2. 19/05/2004 2 What is WS-CAF Specification for Web service transactions based on SOAP A collection of 3 specifications to support information sharing and transaction processing: – Web Service Context (WS-CTX) – Web Service Coordination Framework (WS-CF) – Web Service Transaction Management (WS-TXM) Collaboration of Arjuna Technologies Limited, Fujitsu Software, IONA Technologies PLC, Oracle Corp and Sun Microsystems

3. 19/05/2004 3 Notation participants – cooperating WS in a composite unit of work – share a common context context – data structure containing information pertinent to the shared purpose of the participants coordinator – takes the responsibility for notifying the participants of the outcome – persists the outcomes of the participants, – manages the context interposition – situation when a coordinator represents a set of local participants; then he is registered with another coordinator and thus becomes also a participant – assists in achieving interoperability because the interposed coordinator can also translate a neutral outcome protocol into a platform specific protocol

4. 19/05/2004 4 Positioning the parts the 3 layers comprise a stack of functionality – WS-CTX defines a very simple mechanism that allows multiple Web services to share a common context structure, which is designed to be used independently of the WS-CF and WS-TXM specifications ensures that all Web services participating in a composite application share a common context and can exchange information about a common outcome – WS-CF Defines a coordinator that provides additional features for persisting context operations and guaranteeing the notification of outcome messages to the participants Designed to complement WS-CTX and can be used independently of the WS- TXM specification – WS-TXM defines transaction protocols for ensuring that a common outcome is negotiated with all participants in a composite application defines a protocol for the participants to coordinate outcomes with each other and make a common decision about how to behave, especially in the case of failure Designed to ensure that any given composite application always either reaches successful completion, or reverts to a predictable, known state in failure case of one or more WS

5. 19/05/2004 5 The Context Service (WS-CTX) context is modeled as a Web resource (application specific) Outcome of a coordinated activity or transaction is managed by the context service No mechanisms for negotiating recovery actions in the case of failure

6. 19/05/2004 6 The Coordination Framework Service (WS-CF) coordinator takes responsibility for context management and notifying participants of the outcome of a series of related WS executions (executions are defined as related when they share a common context) The following entities can register as participants with a coordinator: – individual WS – composite applications – coordinators

7. 19/05/2004 7 The Transaction Model Service (WS-TXM) WS-TXM protocols are layered onto the coordinator a set of pluggable transaction protocols are defined to negotiate a set of actions to recover from failure interposition

8. 19/05/2004 8 WS-CAF Relationship between specifications and transaction protocols

9. 19/05/2004 9 author‘s comparison of WS-CAF with other specifications main differences to other specifications in the area of Web service transactions – models transactions at three levels of abstraction to fit different types of business transactions – provides a basic mechanism for context sharing and defines the context as a Web resource that can be independently implemented – defines a neutral, abstract transaction protocol for mapping to existing implementations → achieves broad interoperability through the use of neutral protocols and interposition – any protocol can be used in place/in addition to the neutral protocols defined in WS-TXM; no implementation of a new transaction protocol is required.