| Thanks Drummond! Glad to be on board.
How do the two roles of $is form a single coherent concept? Right now the modifier role (as a passive voice marker modifying the following verb) and the standalone role (as the copulative verb) seem like distinct definitions to me. I realize this is analogous to the English verb "to be" that also serves in both these roles, but is there a philosophical / semantic / formal (take your pick) argument that this should logically be the case in XDI?
One difference I notice between XDI terminology and linguistics terminology is that in the latter, " predicate" means verb together with object, not simply the verb. On May 28, 2010, at 6:27 PM, Drummond Reed wrote: Although I was not able to attend the last TC call, Giovanni and Joseph Boyle (our newest TC member -- welcome Joe!) still held a chat thread. On that thread, they discussed a line of the example PDX document that I posted to http://wiki.oasis-open.org/xdi/PdxExample last week.
The line was right near the start:
$ <-- Pattern: Context Self Descriptor -->
$is$a
($xdi$v$1) <-- Pattern: Context Type -->
($pdx$v$1)
$is($xdi$v$1) <-- Pattern: Context Authority -->
=!1111.aaaa.bbbb.cccc!9999.xxxx.yyyy.zzzz
They were discussing what the predicate "$is($xdi$v$1)" meant.
I thought this was fairly straightforward from the definition of $is as the universal XDI inverse predicate when used as a restriction on any other XDI predicate. Examples:
PREDICATE INVERSE
+father $is+father
+author $is$author
EXAMPLES
=gardner/+father/=drummond
=drummond/$is+father/=gardner
+davinci.code/+author/=dan.brown
=dan.brown/$is+author/+davinci.code
So, the statement
$
$is($xdi$v$1)
=drummond
...is the equivalent to saying
=drummond
($xdi$v$1)
$
..which is simply a way of sayiing that the current XDI context (XDI document, represented by $) is the XDI V1 context of ("belongs to") the personal authority with the identifier =drummond.
This illustrates that the semantics of $is, when used as a restriction (i.e., before ANY other XDI predicate), are simply that it is the inverse of the predicate it restricts (i.e., the entire predicate that follows it).
This is of course true of $is$a, $is$has, and $is$has$a, just like all other inverse predicates.
Hope this helps - I love it that the semantics of $is are the simplest but in some ways one of the most powerful of all XDI predicates.
=Drummond
On Fri, May 28, 2010 at 1:53 AM, Giovanni Bartolomeo <giovanni.bartolomeo@uniroma2.it> wrote:
Hello, Drummond, Bill..
no problem. We just started discussing the PDX sample document and this led to raise some issues... Hopefully during next phcs there will be time to discuss in details these points and the rest of the document.
Kind Regards,
Giovanni
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