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Web Service Resource Framework. http :// www.globus.org/wsrf / WS-Addressing: http://msdn.microsoft.com/library/en-us/dnglobspec/html/ws-addressing.asp. WSMO Presentation Jos de Bruijn Digital Enterprise Research Institute jos.de-bruijn@deri.ie. Agenda. WSRF WS-Addressing

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web service resource framework

Web Service Resource Framework

http://www.globus.org/wsrf/

WS-Addressing:

http://msdn.microsoft.com/library/en-us/dnglobspec/html/ws-addressing.asp

WSMO Presentation

Jos de Bruijn

Digital Enterprise Research Institute

jos.de-bruijn@deri.ie

agenda
Agenda
  • WSRF
  • WS-Addressing
  • How WS-Resource works
  • Implied Resource Pattern
  • WS-Resource lifecycle
  • WS-Resource vs. WS-Context
  • WS-Resource for WSMO?

Jos de Bruijn

jos.de-bruijn@deri.ie

slide3
WSRF
  • Mainly an IBM effort, together with the Globus Alliance and HP
  • Standardization through Global Grid Forum and OASIS
  • Enables discovery of, introspection on and interaction with stateful resources
  • Is based on OGSI (Open Grid Services Infrastructure), using current developments in Web Services standards [remark: not including WS-CAF]
  • WSRF distinguished between a stateless Service and stateful Resources, acted upon by that Service

Jos de Bruijn

jos.de-bruijn@deri.ie

web service resource framework4
Web Service Resource Framework
  • A set of six standards, of which only three have been released:
    • WS-ResourceProperties:
      • how a Web Service interface relates to a WS-Resource
    • WS-ResourceLifetime
      • lifetime management of WS Resources
    • WS-Notification
      • event subscription and notification
  • Unreleased:
    • WS-RenewableReference
      • retrieving updates of invalid endpoint references
    • WS-ServiceGroup
      • heterogeneous collections of Web Services
    • WS-BaseFaults
      • faults / error messages

Jos de Bruijn

jos.de-bruijn@deri.ie

ws addressing
WS-Addressing
  • Defines XML elements to identify endpoints and secure end-to-end endpoint identification
  • Independent of underlying transport mechanism

<wsa:EndpointReference>

<wsa:Address>

http://someOrg.com/aWebService

</wsa:Address>

<wsa:ReferenceProperties>

<tns:resourceID> C </tns:resourceID>

</wsa:ReferenceProperties>

</wsa:EndpointReference>

  • Within WSRF, the endpoint reference is a pointer to a web service, constrained to the context of a specific WS-Resource; the context is opaque to the requestor
  • WS-Addressing states that ReferenceProperties elements must appear as SOAP header elements in messages sent to the service

Jos de Bruijn

jos.de-bruijn@deri.ie

some slides copied from the presentation
Some slides copied from the presentation:

Bringing Grid & Web Services Together

dr. Daniel Sabbah

http://www.globus.org/wsrf/sabbah_wsrf.ppt

Jos de Bruijn

jos.de-bruijn@deri.ie

the ws resource framework model
The WS-Resource framework model

Web Service

Run-time environment

WSDL

Interface

Web

Service

Jos de Bruijn

jos.de-bruijn@deri.ie

the ws resource framework model8
The WS-Resource framework model

Invoking a Web Service

Endpoint Reference

Run-time environment

message

Interface

Web

Service

message

address

Jos de Bruijn

jos.de-bruijn@deri.ie

the ws resource framework model9
The WS-Resource framework model
  • What is a WS-Resource
    • Examples of WS-Resources:
      • Physical entities (e.g.. processor, communication link, disk drive)

or Logical construct (e.g.. agreement, running task, subscription)

      • Real or virtual
      • Static (long-lived, pre-existing) orDynamic (created and destroyed as needed)
      • Simple (one), or Compound (collection)
    • Unique (for the Web Service) - Has a distinguishable identity and lifetime
    • Stateful - Maintains a specific state that can be materialized using XML
    • May be accessed through one or more Web Services

resource

Jos de Bruijn

jos.de-bruijn@deri.ie

the ws resource framework model10

context

The WS-Resource framework model

Using a Web service to access a WS-Resource

Endpoint Reference

Run-time environment

id

resource

id

Interface

Web

Service

message

message

id

address

Jos de Bruijn

jos.de-bruijn@deri.ie

the ws resource framework model11

context

The WS-Resource framework model

Using a Web service to access a WS-Resource

Endpoint Reference

Endpoint Reference

Run-time environment

id

resource

Interface

Web

Service

message

message

id

resource

address

id

Jos de Bruijn

jos.de-bruijn@deri.ie

the ws resource framework model12

id

address

The WS-Resource framework model

Creating / Locating a WS-Resource

Endpoint Reference

Endpoint Reference

Run-time environment

Endpoint Reference

resource

Interface

Web

Service

message

message

address

Web Service either locates or creates a WS-Resource

Jos de Bruijn

jos.de-bruijn@deri.ie

implied resource pattern
Implied Resource Pattern
  • Ensures data encapsulation
  • Describes the way WS-Addressing is used to associate a stateful resource with the execution of message exchanges implemented by a web service.
  • A WS-Addressing EndpointReference must include a ReferenceProperties element, which identifies the resource to be associated with the execution of all message exchange performed using this EndpointReference
  • The stateful resource associated with a given message exchange is treated as implicit execution context for the message request
  • The WS-Resource context is managed by the Web Service

Jos de Bruijn

jos.de-bruijn@deri.ie

ws resource lifecycle
WS-Resource lifecycle
  • Actual creation and destruction and hidden from the requestor
  • WS-Resources created by WS-Resource factories (cf. factory design pattern)
  • WS-Resources are identified using a WS-Resource qualified endpoint reference
  • WS-Resources can be destroyed explicitly by a call from the requestor or after a certain time-out

Jos de Bruijn

jos.de-bruijn@deri.ie

ws resource properties
WS-Resource properties
  • The state of a WS-Resource is expressed as an XML resource property document
  • Requestor can query and modify state through WS message exchanges (e.g. using WS-MetaDataExchange)
  • The resource property document is referred to in the WSDL document
  • Provide can determine how much of the state of the resource to make visible

Jos de Bruijn

jos.de-bruijn@deri.ie

ws resource vs ws context
WS-Resource vs. WS-Context
  • Very interesting email thread on WS-Resource vs. WS-Context (part of WS-CAF):

http://www-unix.gridforum.org/mail_archive/ogsi-wg/2004/01/threads.html#00014

  • WS-Resource seems to ignore WS-Context
  • WS-Context provides a context independent of the service; WS-CTX relates messages with each other
  • WS-Resource provides one endpoint reference (using WS-Addressing) for a resource, which is to be sent to the Web Service, when invoking
  • WS-CTX is used for providing a context for message, without caring what this means; WS-Resource indicates how to retrieve a specific resource; in this sense they are orthogonal

Jos de Bruijn

jos.de-bruijn@deri.ie

ws resource for wsmo
WS-Resource for WSMO
  • Message exchanges in WSMO are stateful
  • It seems to make sense to use WS-Resource in the grounding in the choreography
  • State of a conversation in WS-Resource?
  • We should have a closer look at WS-Context

Jos de Bruijn

jos.de-bruijn@deri.ie