Re: [xdi] Splitting $is into $is and $ref

[Phil Windley <pjw@kynetx.com>]

I like this change because it makes $is much more intuitive.  And I'm in favor of anything that gets rid of $is$is. :)

Drummond, sometime I'd like to understand why $is functions as an inversion function. That doesn't seem intuitive to me. 

--phil--

Phillip J. Windley, Ph.D.
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On Dec 11, 2012, at 1:50 AM, Drummond Reed <drummond.reed@xdi.org> wrote:

Although it's been a very busy week, in my background "cook time" I've been thinking about the suggestion on last Friday's TC call that we split the current proposal for $is predicate behavior (https://wiki.oasis-open.org/xdi/EquivalenceLinks) into two verbs.

The strawman I began playing with this weekend was to break it into:

1. $is = logical equivalence = symmetric, transitive, reflexive
2. $ref = canonical directional equivalence = asymmetric, intransitive, irreflexive

In thinking it through, I realized that this works very cleanly in three ways:

1. Every standalone use of $is as a predicate that we currently have (at least in the XDI graph model document) would become $ref
2. Everyplace where $is is used as the PREFIX for another predicate (e.g., $is$do) would NOT change, i.e., IMHO $is would still work well for this inversion function.
3. This means that the awkward $is$is predicate (needed to identify the equivalence links for root nodes, for example) would now become $is$ref, which reads much better and is certainly more intuitive.

So, at this point I'm very much liking this idea, and I'm ready to write it up as a formal change to the https://wiki.oasis-open.org/xdi/EquivalenceLinks proposal, but first I wanted to post it here on the mailing list for discussion. (I'm also copying this to https://wiki.oasis-open.org/xdi/EquivalenceLinks/Discussion).

=Drummond