- From: Richard Cyganiak <richard@cyganiak.de>
- Date: Thu, 19 Feb 2009 15:53:18 +0000
- To: Michael Hausenblas <michael.hausenblas@deri.org>
- Cc: "www-tag@w3.org" <www-tag@w3.org>, <timbl@w3.org>
Michael, The original question you posed when starting the thread was this: If a1 and a2 are representations of resource a, then can we say anything about how “equivalent” they should be? This question is unrelated to httpRange-14, only minimally related to RDFa, and only somewhat related to fragment ID semantics. Your question can be considered independently of all those other issues, and I think it would be a disservice to the TAG to broaden the question to include all those other areas at once. Your axioms are concerned with the semantics of fragment IDs, that is, what does a URI of the form <xyz#foo> identify? I think this questions is adequately answered by RFC 3986, RFC 2616, and AWWW. It's well- trodden ground and I didn't see anyone articulate a reason for revisiting this part of the architecture. (You might well have such a reason (media fragments?), but don't make us speculate.) Your axioms do not say anything new about * httpRange-14 (which is concerned only with URIs of the form <xyz>, not <xyz#foo>), * RDFa (which requires an update of the HTML/XHTML MIME type declarations, but no changes or clarifications of web architecture), * the representation-equivalence question (which remains the same very thorny a question even if none of the representations define any fragment IDs). Hence I really don't know what you are trying to achieve with your proposal :-( Best, Richard On 19 Feb 2009, at 10:26, Michael Hausenblas wrote: > > Dear TAG members, Tim, Richard, > > Short version: an attempt to defined non-information resources > without using > non-information resource ;) > > Long version: > > In order to contribute in a constructive way to the discussion around > information resources, non-information resources, CN and 200/303 > issues, I'd > like to propose the following, which may be taken as an input to my > previously raised issue around the boundaries of CN in the Web of > Data use > case. To additionally address emerging usage of RDFa, this area has > been > taken into account as well. > > Please note that this is *not* a philosophical approach and I try to > ground > all my terms and only use *existing* protocols, definitions, etc.: > > === > Axiom 1) A URI containing a fragment identifier as of RFC3986 [1] > identifies > a 'thing', that is, a resource which essential characteristics are not > conveyed in a message as opposed to an information resource as of > AWWW1 [2], > unless otherwise stated. > > Axiom 2) Iff the media type of a representation obtained by > dereferencing a > URI (that is, performing an HTTP GET on the URI) defines the > semantics of > the fragment identifier, the resource is an information resource as > of [2]; > this is the case 3 in [3]. > > Axiom 3) Iff the authoritative party as defined in section '2.2.2.1. > URI > ownership' of [4], that is the one who can claim URI ownership, > explicitly > states that fragment identifier semantics throughout different > representations are sufficiently consistent, the resource is an > information > resource as of [2]; this is the case 1 in [3]. > > Axiom 4) An authoritative party can explicitly state fragment > identifier > semantics consistency by using POWDER's describedby property as of > [5] along > with HTTP Link: header as of [6] or by embedding RDF as of [7]. > === > > Please note the following: The intention is to keep the current > definition > of IR as of the AWWW1 and clearly define what else is possible, > hence to > make related (sometimes questioned and IMHO underspecified > definitions such > as for example found in httpRange-14) more usable in a practical > context. > The axiom 1 actually asks people to use frag-ID-URIs as the (one and > only) > default to identify 'things', however, axiom 2 - 4 allow to create > exceptions based on an explicit set of actions. Further, axiom allows > (currently) two ways to 'announce' exceptions, on the HTTP layer or > on the > representation layer - this is open to discussion and should/will be > extended. > > @Tim: Do you think this helps in getting closer to a written > explanation of > your often articulated thoughts re 'sameness' of information > obtained from > resources, as e.g. in [8]? And also: does this solve our issue wit > RDFa as > discussed in [9]? > > @Richard: Are the axioms consistent with the outcome of your > analysis in > [10]? > > Cheers, > Michael > > [1] http://tools.ietf.org/html/rfc3986#section-3.5 > [2] http://www.w3.org/TR/webarch/#def-information-resource > [3] http://www.w3.org/TR/webarch/#frag-coneg > [4] http://www.w3.org/TR/webarch/#URI-collision > [5] http://www.w3.org/2007/05/powder-s#describedby > [6] http://tools.ietf.org/html/draft-nottingham-http-link-header-03 > [7] http://www.w3.org/2001/tag/doc/selfDescribingDocuments#UsingRDFa > [8] http://chatlogs.planetrdf.com/swig/2009-02-09#T15-09-20 > [9] http://esw.w3.org/topic/RDFa_vs_RDFXML > [10] http://lists.w3.org/Archives/Public/semantic-web/2007Dec/ > 0157.html > > -- > Dr. Michael Hausenblas > DERI - Digital Enterprise Research Institute > National University of Ireland, Lower Dangan, > Galway, Ireland, Europe > Tel. +353 91 495730 > http://sw-app.org/about.html > http://webofdata.wordpress.com/ >
Received on Thursday, 19 February 2009 15:54:01 UTC