Bracketing Refs [Authority Resolution]

["Steven Churchill" <steven.churchill@xdi.org>]

This proposes a bracketing scheme for outputting Refs during the authority
resolution phase. This provides a human and machine readable way to
negotiate a nested Ref resolution hierarchy.

<XRDS>
    
    <XRD-A /> 
    <RefRes>
        <XRD-E />
	  <RefRes>
            <XRD-H />
    	  </RefRes>
        <XRD-F />
        <XRD-G />
    </RefRes>
    <XRD-B />    
    <XRD-C />
    <RefRes>
        <XRD-I />
    </RefRes>
    <XRD-D />

</XRDS>


The <RefRes> element is used to bracket the XRDs necessary to resolve a Ref.
The <RefRes> element MUST appear between two <XRD> elements. (It would never
fall at the beginning or end, and two <RefRes> elements would never appear
together.)

The final <XRD> in the <RefRes> is that used for the subsegment resolution
of the <XRD> that follows the <RefRes>. Therefore, in the example above, the
subsegment resolution XRD chain is:

    G, B, I, D

Note that, since the <RefRes> "replaces" the preceding <XRD> from a
subsegment resolution standpoint, the number of (top-level) XRDs in the
<XRDS> is always equal to the number of authority subsegments.

~ Steve