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


The issue is still open, but I am not sure we have nails the exact problem yet.

If you recall about 6 months ago we had a discussion about whether Links in host-meta apply to individual resources belonging to the host under LRDD. According to the host-meta spec, they do, but LRDD I explicitly chose to ignore them for the purpose of looking for descriptors. A few days ago Dirk raised the same questions.

We had all these issues before with the text-based host-meta but they were just not that obvious because we were unable to apply all the thinking that went into XRD there. But now that we reformatted host-meta to use XRD, it all surfaced.

The two main questions are:

1. What is a 'host' (or 'site' or 'authority' etc.)?
2. How do we identify it?

So far we defined host as either:

1. Any resource belonging to the combination of domain/port/protocol (i.e. a set), or
2. An abstract concept of authority restricted by domain/port and possibly protocol

A Link to one has a very different meaning than the other. In fact, I don't know what a Link means for #2...

If we decide a host is a 'set', we should find a way to describe a set of URIs (which will be useful for other purposes). If we decide a host is a resource (of some sort), we should find a URI to identify it.

I don't think there is right or wrong here. It is just a question of which option is easier/more productive/reusable.

EHL


> -----Original Message-----
> From: Drummond Reed [mailto:drummond.reed@cordance.net]
> Sent: Tuesday, June 30, 2009 10:47 PM
> To: Eran Hammer-Lahav; 'XRI TC'
> Subject: Subject of a host-meta XRD (was: <SubjectTemplate>)
> 
> 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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