RE: [xri] ED04 synonym proposal (was RE: [xri] CID changes in wd11)

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

Wil, you wrote:

> I understand and agree that EquivID is p2p and non-directional, while
> MapToID/MapFromID are directional. I also understand that it would be
> Nice to be able to express an AKA relationship using a non-directional
> element. However, I'm not sure if the use case is a strong one.
> Generally, I would prefer to leave these to an extension (the X in XRDS)
> since it doesn't affect the core resolution behavior; my compiler has
> detected an "unreferenced local variable named EquivID".

My preference is strongly to include EquivID in the base XRD namespace
because this is the only means we will be providing to express
non-directional, p2p relationships between identifiers. Again, the purpose
of this element is to enable direct equivalence mappings between identifiers
with no overloading of either: a) resolution semantics, or b) mapping
(replacement) semantics.

To leave this element out of the base XRD namespace would be to invite lots
of non-standard ways to express a very basic concept.

> I also don't understand how you could use EquivID to express directional
> equivalence without MapToID/MapFromID. Unless, of course, you encode
> directionality into an attribute of EquivID, but that IMO is less
> preferable to having separate elements.

I'm not sure who may have given the impression that EquivID could be used to
provide directional equivalence; I've always said that its purpose was
non-directional, and that directional equivalence should use
MapToID/MapFromID. I agree with you that separate elements for
non-directional and directional equivalence is much more precise, and makes
it easier for communities and applications to set policies around their use
of these synonym types.

=Drummond