Subject of a host-meta XRD (was: <SubjectTemplate>)

["Drummond Reed" <drummond.reed@cordance.net>]

Eran,

I knew as soon as the question "What's the subject of a host-meta XRD?" came
up that we were headed into W3C httpRange-14 territory. For those who have
never heard about this "Web identity crisis", see:

	http://www.w3.org/2001/tag/doc/httpRange-14/2007-05-31/HttpRange-14 
	http://norman.walsh.name/2005/06/19/httpRange-14 
	http://www.garshol.priv.no/blog/125.html 

There are dozens more references where those came from, as I'm sure those
who have stepped into this quicksand know. Just Google "httpRange-14".

So I'm not going to try to give any philosophical answers here, only
practical ones. On that basis, my observations:

1) Both the <XRD:SubjectTemplate> suggestion (see below) and the Powder
approach (essentially another way of desribing a URI template using
individual XML elements for each constraint) seem like reasonable options. I
prefer SubjectTemplate because it's less complex. But I'm not sure what the
SubjectTemplate value would be that describes "the authority for this
domain" vs. any specific resource in that domain. Would it just be a
wildcard?

2) A second option is to use either a fragment, or an empty fragment. I
prefer the latter for this particular use case. In other words, if
http://example.com identifies a specific information resource (e.g., the 200
response you get back), then http://example.com# could describe the abstract
concept of http://example.com (a non-information resource).

2) A third option -- mentioned frequently in the httpRange-14 debate -- is
using another URI scheme intended exclusively to represent non-information
resources. (Hmmmm, where could we find something like that? ;-) Of course,
it's ironic that due to W3C TAG's input, XRI is no longer actually another
URI scheme, but an identifier syntax that is bound to a base URI to produce
a valid URI. I posted earlier about what the bound http: XRI that described
"the current authority" would look like: http://xri.net/$. 

In any case, all three of these options would appear to work. Have you
decided on one? Is the issue still open?

=Drummond 

> -----Original Message-----
> From: Eran Hammer-Lahav [mailto:eran@hueniverse.com]
> Sent: Sunday, June 28, 2009 12:37 PM
> To: XRI TC
> Subject: [xri] <SubjectTemplate>
> 
> This idea isn't new but given the need to solve the host-meta Subject use
> case, I would like to know what others here think about it.
> 
> EHL
> 
> -----Original Message-----
> From: uri-request@w3.org [mailto:uri-request@w3.org] On Behalf Of Eran
> Hammer-Lahav
> Sent: Sunday, June 28, 2009 12:32 PM
> To: Erik Wilde; uri@w3.org
> Subject: RE: URI for abstract concepts (domain, host, origin, site, etc.)
> 
> Using a URI template is one option being considered (XRD already has a
> <URITemplate> element under <Link> so the syntax is already part of XRD).
> However, that requires either creating a new element (like
> <SubjectTemplate>) or changing the XML schema type for <Subject> which
> currently does not allow anything but valid URIs.
> 
> But before we consider that, I wanted to see if there was an easy solution
> for describing such resources with a URI.
> 
> EHL
> 
> > -----Original Message-----
> > From: uri-request@w3.org [mailto:uri-request@w3.org] On Behalf Of Erik
> > Wilde
> > Sent: Sunday, June 28, 2009 11:43 AM
> > To: uri@w3.org
> > Subject: Re: URI for abstract concepts (domain, host, origin, site,
> > etc.)
> >
> > hello.
> >
> > Eran Hammer-Lahav wrote:
> > > Let me try explaining my use case again, this time without any
> > overloaded terminology or proposed solutions.
> > > XRD is a document format for describing resources. It looks like
> > this:
> > > <XRD>
> > > 	<Subject>http://example.com</Subject>
> > > 	<Type>http://example.org/type/blog</Type>
> > > 	<Link>
> > > 		<Rel>author</Rel>
> > > 		<URI>http://example.com/author</URI>
> > > 	</URI>
> > > </XRD>
> > > Without getting too much into XRD, this short descriptor describes
> > the resource identified by 'http://example.com'. It includes one type
> > indicator (a made up example meant to mean this resource is a blog),
> > and one link to the author's page.
> > > I want to use this document format to describe rules that apply to
> > all resources which belong to an HTTP host (as defined by 2616: a
> > domain/address and port combination). The problem is, <Subject>
> > requires a URI and currently there is no way to identify this set of
> > resources (http://domain:port/*) as a valid URI.
> > > What I don't want to do is use an exception such as 'if the URI
> > begins with X, treat it as a rule and not a valid URI'...
> >
> > given this new description, isn't what you're looking for a URI
> > template
> > language for XRD? maybe not exactly the one currently proposed by
> > http://tools.ietf.org/html/draft-gregorio-uritemplate-03, but isn't
> > that
> > close to what you want? a template notation would also nicely address
> > the case mentioned already where the host scope would be too general.
> > but then again, a URI template is not a URI, so you could use it in the
> > context of XRD, but not as a standalone URI....
> >
> > cheers,
> >
> > erik wilde   tel:+1-510-6432253 - fax:+1-510-6425814
> >         dret@berkeley.edu  -  http://dret.net/netdret
> >         UC Berkeley - School of Information (ISchool)
> 
> 
> 
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