- From: Xiaoshu Wang <wangxiao@musc.edu>
- Date: Fri, 20 Feb 2009 15:02:23 +0000
- To: Michael Hausenblas <michael.hausenblas@deri.org>
- CC: "www-tag@w3.org" <www-tag@w3.org>, "timbl@w3.org" <timbl@w3.org>, Richard Cyganiak <richard@cyganiak.de>
Michael Hausenblas wrote: > Dear TAG members, Tim, Richard, > > Short version: an attempt to defined non-information resources without using > non-information resource ;) > I am not sure your proposal will work (see below). But here is the fundamental question: what is the purpose? Unlike if we know "x is a Human", we can infer that "x has (at least) one head", I wonder what more "x is an IR" tells me except "x is an IR". The original intension of defining IR, I believe, is to avoid ambiguous identity. But the solution is always using different URIs for different things. Defining something like IR does not help. > 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. > This gives a syntactic definition of "Thing" (which I believe is non-IR thing). It is no different to name it as, say "hash-thing". Hence, we can infer from a "hash-thing" that "not all essential characteristics is conveyed in the message" so it grants "hash-thing" an open world semantics. But the implication is that "slash-thing", i.e., things denoted by a slash URI, should not be talked about because it is closed. Otherwise, what is the difference between "hash-thing" (IR) or "slash-thing" (non-IR). Furthermore, the Web is defined by three things -- URI, Representation, and Resource(things). In other words, these are the three things we know about the Web at its fundamental level. The syntactic definition of a URI can be used to distinguish these three entities (it would be ideal and convenient if we do so, though not necessarily). Using a syntactic definition for anything else would suggest that either (1) the Web requires additional founding concept or (2) it would violate the URI's opacity principle. > 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]. > Define the "define"? > 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]. > Another ambiguous word "sufficiently"... > 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]. > This is even more trouble-some to me. If the IR makes as a foundation concept of the Web, this axioms essentially making POWDER, HTTP LINK, RDFa at the same fundamental level of the AWWW. > === > > 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 > >
Received on Friday, 20 February 2009 15:03:21 UTC