Joseph Boyle (Inactive) added a comment - 03/Sep/14 11:56 PM - edited $is is documented at https://wiki.oasis-open.org/xdi/EquivalenceRelations I don't see $is() in the wiki except in the ABNF. https://lists.oasis-open.org/archives/xdi/201311/msg00016.html "going to an empty path to represent the outer root created a problem for inverse contextual statements, since the inverse contextual predicate would become just $is, i.e., an identity equivalence statement. Markus and I explored this and decided that it did in fact work semantically if the object of the inverse contextual statement was the complete context. For example: =markus//<+name> <+name>/$is/=markus<+name> 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."