[security-services] URNs for SAML spec identifiers

The SAML core spec draft (draft-sstc-core-25.pdf) specifies a number of
URIs to identify protocol elements, including XML namespaces (eg lines 180
and 183) and other items such as confirmation methods (section 7.1, lines
1449 and following).  These are currently http: URLs (acknowledged as
temporary), but I suggest it would be better to use URNs in the urn:oasis
namespace as defined in RFC 3121.  I note that the DSML 2.0 document uses
a base namespace of "urn:oasis:names:tc:DSML:2:0:core" and so is a good
precedent.  I suggest for SAML a base of:

  urn:oasis:names:tc:SAML:1.0

Even though the TC isn't named "SAML" it seems like this string would be
both concise and well-understood.  But Karl (I suppose) should make this
call.

Given the above, the assertion and protocol URNs could be:

  urn:oasis:names:tc:SAML:1.0:assertion
  urn:oasis:names:tc:SAML:1.0:protocol

and perhaps the confirmation method identifiers could be:

  urn:oasis:names:tc:SAML:1.0:cm:artifact
  urn:oasis:names:tc:SAML:1.0:cm:holder-of-key

etc.  And the Action namespace identifiers in section 7.2 (lines 1520 etc)
could be:

  urn:oasis:names:tc:SAML:1.0:action:rwedc

etc.

 - RL "Bob"