Proposed resolution to WSRF 174 - references to instances of MDDs

[Ian Robinson <ian_robinson@uk.ibm.com>]

On the TC call on Mon Apr 3 we discussed an alternative resolution to that
originally proposed for issue 174 for obtaining the values of metadata
descriptor document instances that might be specific to a WS-Resource
instance and potentially dynamic (hence factored as a RP). Instead of
introducing an additonal RP that contains the value of an RMD instance doc
for a WS-Resource, this proposal changes the type and some semantics of the
existing MetadataDescriptorRef RP (which contains a reference to an RMD
instance doc).

Regardless of which solution we follow, we need to start by fixing a
problem in theRMD wd-08 draft so that:

Line s 897/898,
      <xsd:element name="MetadataDescriptor"
                   type="wsrmd:MetadataDescriptorRef"/>
should be
      <xsd:element name="MetadataDescriptorRef"
                   type="wsrmd:MetadataDescriptorRefType"/>

This resolution then proposes the further change that the definition of
MetadataDescriptorRefType be changed to wsa:EndpointReferenceType. The
value of MetadataDescriptorRef is then an EPR to a "metadata WS-Resource"
associated with the original WS-Resource.

The description of this element should be changed as follosw:

"
The constraints on this element are as follows:

/wsrmd:MetadataDescriptorRef
This element is an EndpointReference to a "metadata WS-Resource" associated
with the target WS-Resource. This metadata WS-Resource has a resource
properties document that is the MetadataDescriptor document of the target
WS-Resource. The metadata WS-Resource MUST support the
wsrf-rpw:GetResourcePropertiesDocument message exchange and MUST respond to
such a request by returning the MetadataDescriptor document that describes
the target WS-Resource.
"
The description of
"/wsrmd:MetadataDescriptorRef/@metadataDescriptorLocation" should be
removed from this section.


<TC discussion not intended to be included in the resolution>

In general, if a WS-Resource "A" has an associated metadata WS-Resource
"mdA" then the resource properties document associated with mdA *is* the
metadescriptor document associated with A. Information about A's
(potentially dynamic) instance metadata can then be queried (and
potentially updated) using normal WSRF-RP message exchanges targeted at the
mdA EPR.
A constraint on metadata WS-Resources, above and beyond that of general
WS-Resources, is that they MUST support the GetResourcePropertyDocument
message exchange (which is optional for general WS-Resources). The
constraint needs to be stated in the RMD doc in the section "10.2 Using
Resoure Property Elements to expose MetadataDescriptors "

</TC discussion not intended to be included in the resolution>


The schema should then define:
    <!--
    <MetadataDescriptorRef>
      <wsa:Address>URI</wsa:Address>
      <tns:SomeReferenceParameter>xsd:any<tns:SomeReferenceParameter> ?
    </MetadataDescriptorRef>
    -->
      <xsd:complexType name="MetadataDescriptorRefType" >
        <xsd:complexContent>
          <xsd:extension base="wsa:EndpointReferenceType">
          </xsd:extension>
        </xsd:complexContent>
      </xsd:complexType>

    <xsd:element name="MetadataDescriptorRef"
                   type="wsrmd:MetadataDescriptorRefType" />





Regards,
Ian Robinson