- From: Eran Hammer-Lahav <eran@hueniverse.com>
- Date: Sun, 28 Jun 2009 11:09:53 -0700
- To: "ashok.malhotra@oracle.com" <ashok.malhotra@oracle.com>
- CC: "apps-discuss@ietf.org" <apps-discuss@ietf.org>, "www-tag@w3.org" <www-tag@w3.org>, URI <uri@w3.org>
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'... EHL > -----Original Message----- > From: ashok malhotra [mailto:ashok.malhotra@oracle.com] > Sent: Saturday, June 27, 2009 6:08 PM > To: Eran Hammer-Lahav > Cc: apps-discuss@ietf.org; www-tag@w3.org; URI > Subject: Re: URI for abstract concepts (domain, host, origin, site, > etc.) > > Hi Eran: > Trying to understand your proposal. > By 'abstract' do you mean URIs for which a representation cannot be > retrieved? > So, perhaps, a chair? > > My assumption was that for such resources you want to retrieve the > metadata. > To do that you do a GET which returns a 'Not Found' as well as a Link > Header. > > Of course, if you know syntactically that the resource does not have a > representation > you can save one access and go directly for the metadata. > > Is that where you are going? > > All the best, Ashok > > > Eran Hammer-Lahav wrote: > > LRDD [1] defines a way to link a descriptor (metadata, information > about, etc.) to a resource. It keeps the document format of the > descriptor out of scope, leaving it up to existing formats (XRDS, XRD, > POWDER, Metalink, etc.) and new format to address. > > > > Most of these descriptor formats include an element which indicates > what the document is about - the subject of the descriptor. XRD > includes the <Subject> element for this purpose with xs:anyURI as its > type. I believe POWDER uses RDF's 'about' attribute in a similar way > IIRC. > > > > We have some use cases in which the subject of the descriptor does > not have a URI available. > > > > LRDD uses a well-known-location document (/host-meta, soon to be > replaced with /.well-known/host-meta) to store information about the > abstract host resource (the combination of domain name and port number, > potentially also including protocol). Over the past few years, ad-hoc > protocols have been abusing the root resource URI to mean something > beyond just the root resource of a domain - basically as a placeholder > for information about the entire domain or host. > > > > The lack of URI for such concepts is preventing descriptor formats > from being used here because there is no valid URI available to insert > into the subject container. While no representation is expected for > such abstract concepts, within the context of descriptors, being able > to reference them is critical. > > > > The use case at hand is using XRD as the document format for host- > meta. Host-meta describes attributes of the host which by itself does > not currently have a URI. We need to figure out what to put in the > host-meta document's <Subject> element which has direct impact on the > trust profile and signature (but is outside the scope of this > discussion). > > > > So far I could only come up with two options: > > > > 1. Make a special case exception that when the subject is > http://______/.well-known/host-meta, it is treated differently than any > other URI in that it means the XRD is not about that URI (the host-meta > document itself), but about the abstract host resource located at > ______. > > > > 2. Define a new kind of URI that can be used for abstract entities > such as "host" or "domain", but which is not an http URI because that > will bring us right back to #1. > > > > I would like to ask for feedback on the idea of proposing a new URI > scheme or a new URN namespace for this purpose, something like > 'abstract'. > > It will look something like this (please focus on the idea, not the > syntax of the examples): > > > > urn:abstract:domain:example.com > > urn:abstract:host:example.com:8080 > > urn:abstract:origin:example.com:8080:http > > > > or > > > > abstract://example.com/domain > > abstract://example.com:8080/host > > abstract://example.com:8080:http/origin > > > > Any comments, feedback, or concerns would be greatly appreciated. > > > > EHL > > > > [1] http://tools.ietf.org/html/draft-hammer-discovery > > > > > > > >
Received on Sunday, 28 June 2009 18:10:36 UTC