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Subject: Re: [xdi] 2 key proposals coming out of the last TC telecon & subsequent discussions

On Tue, Nov 12, 2013 at 10:23 AM, Joseph Boyle <planetwork@josephboyle.net> wrote:
Question about #2:
Are we adopting your proposal to view XDI statements as relative to a local root, rather than absolute (that is, relative to the global outer root)?

Short answer: after my discussions with Markus about it this weekend, no. The rule is that all XDI statements are relative to the global outer root. Every XDI graph contains that node, i.e., it is the starting point of all XDI graphs.
Would inverting a contextual statement give different results with respect to the local root, or with respect to the outer root?

Per the above, no.
Is this the difference between /$is/ and /$is()/?

No. Again, per my long discussion with Markus this weekend, $is and $is() retain exactly the semantics we have defined for them for several years now, i.e.:
  1. $is used alone is the identity equivalence predicate; used as a prefix it is the inversion prefix.
  2. $is() is the inverse contextual statement predicate—the subject is the child context and the object is the parent context.

On Nov 12, 2013, at 12:08 AM, Drummond Reed <drummond.reed@xdi.org> wrote:


On last Friday's TC call we discussed that going to an empty path to represent the outer root created a problem for inverse contextual statements, since the inverse contextual predicate would be come just $is, i.e., an identity equivalence statement. Markus and I explored this and decided that it did in fact work semantically if the object of the inverse contextual statement was the complete context. For example:


However after much discussion we felt that this was a different semantic that our current inverse contextual predicate, which only requires the parent context as the object. And we decided that we still needed this semantic. Thus our conclusion was that we should to keep $is() as the inverse contextual predicate. Our logic is that the parentheses become necessary simply because they enclose the actual XDI address of the outer root (which is empty) as a cross-reference so that it can be described by the inverse predicate $is.

So that means no change in our current syntax for inverse contextual predicates, e.g.:


Please post if you have any further thoughts about either of these two conclusions.


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