Transcript WS CF - WSMO

Web Services Coordination
Framework
WS-CF
http://developers.sun.com/techtopics/webservices/wscaf/wscf.pdf
Presented by: Francisco Martin-Recuerda
Overview
• Introduction
• Architecture
• WS-CF Coordination Protocols
• Open Issues
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Introduction
• WS-CF specifies a software agent to handle context
management through coordinator.
• Coordination is necessary for distributed applications
(i.e. Web Services in choreography)
• Defines a Web Service Coordinator:
– Context Management.
– Maintain a repository of participants.
– Guarantee that the participants get the results of the
coordinated interaction.
– Uses SOAP to encode messages and WSDL to use a
synchronous invocation style for sending requests.
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Introduction (II)
WS-CF
Web Services Stack
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Architecture
• Web Service Coordinator:
– Provides an interface for the registration of participants and activities.
– Disseminates information to a number of participants and guarantees
that all of them get the information.
– Manages the context.
– Context information can flow inside messages sent to the participants.
– A coordinator can be also a participant to another coordinator,
extending the ability to interoperate accross application domain.
• Participants:
– cooperating Web Services in a composite unit of work
– share a common context
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Architecture (II)
• Activity:
– Represent a defined set of tasks with a set of related coordination
actions.
– Involved one or more elements (participants that interacts through a
coordinated).
• Coordination Service:
– Defines and provides a processing pattern (model).
– Example: ACID transaction service provides a protocol that defines a
sequence processing: Prepare, Commit and Rollback.
– Also defines how activities are coordinated (activities can cooperate
with each other).
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Architecture (III)
• Protocol Configuration and Negotiation:
– Defines a protocol negotiation between web services to
determine which Coordination Service model will be used.
– Determines which protocol message exchange will be
used.
– Defines a method to communicate the results of a
process.
– Defines the message interactions between the coordinator
and its participants.
– Unambiguously identied by a URI.
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WS-CF Coordination Protocols
Coordinator to participant interactions
– Messages can start the execution of a particular task
for a specific participant or
– Ask for the current state of the execution or
– Return or distribute results of the execution of
some process.
Service to coordinator interactions
– Basically defines how a service can ask to a
coordinator to register or unregister participants for
an specific activity.
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WS-CF Coordination Protocols
Client to coordinator
– Basically defienes how a client (user) of the
coordination service can obtain the status of the
coordination or ask it to perform coordination.
Interposition
– As we mentioned before, coordinator can be also
participants for other coordinator.
– Reduces overhead using proxy coordinator (or
subordinate coordinators).
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Open Issues
•
•
•
•
Guarantee security and confidentiality.
Audit trail (log of actions).
Protocol completeness guarantee.
Quality of Service.
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