Web Service Referencing And Resource Identification Anish Karmarkar Oracle Corp.

Overview Web Service Reference – What is it? – EPR – WSRef (part of WS-MessageDelivery) Identifying Resources – Implicit Resource Pattern l Using EPR l Using WSRef – Explicit Message Parts

Web service Reference: What? Identify and reference a Web service Allow passing of references in messages Must contain information to access and invoke a Web service – Format of messages – Operations – Protocol – Endpoint Must be WSDL centric URI is not a Web service Reference

EPR: cannot be used to reference a Web service URI is the only thing that is required Is not WSDL centric Invents new constructs Conflates referencing mechanism with reference properties

WS-MessageDelivery: WSRef New W3C Note located at – messagedelivery / messagedelivery / WSRef – WSDL centric – No new constructs – Very little change needed for the infrastructure/tools/runtime – Does not overload a reference with reference properties – In-line with WSDL 2.0

Identifying Resources WS-RF specs require that a resource be identified in a Web service interaction Three ways to do this – Implicit Resource Pattern using EPR – Implicit Resource Pattern using WSRef + a standard SOAP header block – Explicit message part (parameter)

Choice A: Implicit Resource Pattern (EPR) Tightly bound to EPR Resource identifiers sent as SOAP header blocks (but bound to reference properties) Identifiers not explicitly expressed in WSDL Cannot be composed/discovered

Choice B: Implicit Resource Pattern (WSRef) Replace EPR with WSRef Pass resource identifiers in a SOAP header block – Repurpose WS-Context OR – TC creates a new header block (for e.g., wsrf:ResourceIdentifier) Allows the infrastructure to deal with the header block Clients are not required to send every arbitrary header (not known in advance) that the Server chooses

Choice C: Explicit identification of the Resource in WSDL Expose the schema of the resource identifier Specify the resource identifier in the WSDL description as a message part Principle: If something can be described in WSDL – it should be Allows composition/discovery

Summary/Message WSDL centric Don’t invent new constructs unless needed WSRef – a Web service Reference is an ideal candidate to be used in WS-RF TC should discuss the merits of EPR and WSRef TC should discuss choices available for resource identification

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