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Web Services Composite Application Framework (WS-CAF)

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. What is WS-CAF. Specification for Web service transactions based on SOAP

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Web Services Composite Application Framework (WS-CAF)

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  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. 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. 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. 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. 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. 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. 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. WS-CAFRelationship between specifications and transaction protocols

  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.

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