XRI subject matching

[Will Norris <will@willnorris.com>]

There has been a bit of discussion on the thread list XRD Subjects,  
most around the ongoing problem of what to do for host-meta  
documents.  To date, host-meta has been the only use-case for the  
match attribute on Subject, but I wanted to remind everyone of another  
-- XRI matching.  Drummond and John were supposed to talk about this a  
bit offline, so I'll let them respond with what they've come up with,  
but very preliminary discussions I had with Drummond indicated that  
the match attribute would be very useful for XRI matching.  I'll be  
the first to admit I don't fully grok XRI syntax, much less the latest  
3.0 draft, so someone can explain more if necessary.  All I do know  
however, is that the following two URIs represent the same  
"=willnorris" XRI:

   http://xri.net/=willnorris
   http://xri.fullxri.com/=willnorris

There is no way to know that these should be considered equivalent  
without some special processing rules.  They are certainly not  
equivalent strings, and a "beginswith" comparison doesn't work  
either.  This means that XRI Resolution 3.0 will need to define a new  
value for the match attribute that means, "This thing is an XRI.   
Compare it against other URIs using the following rules...".  If we  
drop the match attribute in favor of something like <Host> for host- 
meta, then we're leaving XRI resolution out in the cold.  While I  
believe that "beginswith" Subject matching for host-meta is the worst  
possible solution (except of course for all the others), I want to  
make sure folks remember that we do have at least one other use case  
to keep in mind.

-will