another schema

This schema has a "minimal core", and an <Options> where anything else can 
be stuffed in.  The currently defined options are:
  - RequestID
  - ApplicationProfile
  - ClaimedIdentity
  - SignatureTimestamp - if present, a timestamp over the signature is added
  - ContentTimestamp - " "  over the content is added
  - KeySelector - which key to use
  - ReturnDocumentWithSignature - instructs the server to insert signature 
into a document and return that document
  - SignatureProperties - Signed/Unsigned properties to add to signature

Example:

<SignRequest>
	<Options>
		<ClaimedIdentity>abcdef</ClaimedIdentity>
		<ApplicationProfile>urn:ietf:hello</ApplicationProfile>
		<IntendedAudience>
			<Recipient></Recipient>
		</IntendedAudience>
		<SignatureTimestamp/>
		<ContentTimestamp/>		
	</Options>
	<SignedReferences>
		<SignedReference WhichInputDocument="A"/>
		<SignedReference WhichInputDocument="B"/>
	</SignedReferences>
	<InputDocuments>
		<Document ID="A">
			<Data MimeType="text/xml">fQgRO4g3SXI=</Data>
		</Document>
		<DocumentURI ID="B">
			<URI>http://trevp.net</URI>
		</DocumentURI>
	</InputDocuments>
</SignRequest>

The last emails between Rich and I mention some features of this that might 
be controversial.  Other opinions or different ideas or approaches or 
anything are welcome..

http://www.oasis-open.org/apps/org/workgroup/dss/download.php/3621/oasis-dss-1.0-core-schema-perrin-05.xsd

Trevor