OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.


Help: OASIS Mailing Lists Help | MarkMail Help

xdi message

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]

Subject: $is is the universal inverse restriction

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 -->
($xdi$v$1) <-- Pattern: Context Type -->
$is($xdi$v$1) <-- Pattern: Context Authority -->

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:

+father                        $is+father
+author                       $is$author




So, the statement


...is the equivalent to saying


..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.


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,

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]