XRD:Link:TargetSubject and XRD:Link:SourceAlias

["Drummond Reed" <drummond.reed@cordance.net>]

I have an action item per the minutes I just sent out to explain new
proposed element names for the two XRD link child elements we discussed on
today's telecon.

These names did not occur to me until after I had time to cook on the
discussion.

In retrospect, they are relatively obvious because they both follow this
formula:

	XRD:Link:[link-direction-name][resource-identifier-type]

By "link direction name", I mean this: what's hard about the semantics of
these two element names is that they name identifiers that are relative to a
link. The first element is naming an identifier for the target of the link.
The second element is naming an identifier for the source of the link.

We don't have any other elements that need to include the source/target
directionality in order to be semantically clear, so that's why this
discussion has taken so long. However, unless someone has better terms, the
terms "source" and "target" have well understood semantics when it comes to
link directionality.

Secondly, by "resource identifier type", I mean this: we have established at
the XRD level semantics for two types of identifiers for a resource:
Subject, which is a canonical identifier for the resource, and Alias, which
is any other identifier for that resource.

Put these two together and you end out with precise semantics for these two
elements:

1) <XRD:Link:TargetSubject>

Cardinality zero-or-one; type anyURI. If present, it MUST contain an
identical value to the contents of the <XRD:Subject> element of an XRD
describing the link target. (Again, the use case for this element is trust
verification of synonym mappings.)

2) <XRD:Link:SourceAlias>

Cardinality zero-or-more; type string. If present, it MAY contain an
identical value to the contents of an <XRD:Alias> element in the source XRD
OR it may contain any other identifier needed to identify the resource
described by the source XRD in the context of the link target resource.