- From: Williams, Stuart <skw@hp.com>
- Date: Tue, 30 Sep 2003 12:02:01 +0100
- To: "'Larry Masinter'" <LMM@acm.org>
- Cc: www-tag@w3.org
Hi Larry, > -----Original Message----- > From: Larry Masinter [mailto:LMM@acm.org] > Sent: 30 September 2003 04:46 > To: 'Williams, Stuart' > Cc: www-tag@w3.org > Subject: RE: Use of metadata in URIs > > > (trying to keep this short) Lest it need be said, I very much appreciate your input, thanks. > > > I was actually trying to explore from two perspectives... that of an > > assignment authority (and the infrastructure under their control, eg. origin > > servers - and maybe CDNs); and that of 'observers' of URI assigned outside > > of their own authority. It seems to me that the 'freedoms' to read something > > into a URI are different from each perspective. > > The finding says it is intended to address two related questions: > > 1. What, if anything, can be inferred from a URI used to > identify a resource? 2. What information about a resource can > or should be embedded in a URI used to identify that resource? > > Neither of these questions seems to be posed from the point > of view of an 'authority' who might 'assign' a URI. I see the first question as taking the observers perspective and the second as taking the assignment authority's perspective. > URIs are used in communication. There is the agent (person or > software) that utters (publishes, sends) the URI, and there > is the agent (person or software) that receives and interprets the URI. Agreed. > In some cases, there might also be some process or procedure > involving some agents that might cause a URI to be associated > with some resource, Ok... > e.g., a webmaster at a web site > configuring a web server and a user of that site storing some > file in a directory that the configuration points to. But the > intent and roles of these agents ('authorities', if you like) > aren't really involved in the conversation about 'what, if > anything, can be inferred'. Ok... maybe... but there is (at least the perception of) a chain of specifications through which authority is delegated - rooted in the RFC2396 - and that is (or can be) involved in the behaviours that get programmed into these agents. Maybe this is a mis-perception, which I think is the position that you are taking. If that's the case I think it is quite widely held, and I don't know where the concensus actually lies, even amongst the small community cited as authoring 2396 - never mind the large community (including myself) that may have read too much into it. > When I tell you I have a comment about > http://www.w3.org/2001/tag/doc/metaDataInURI-31.html, our > mutual understanding of the meaning of that URI > doesn't depend on whoever has "control" or "authority" over "www.w3.org", > except for our mutual belief that when we poke that URI we will get the > same reaction. It's an operational understanding. Ok... yes... an operational understanding that there will be some consistency about representations retrieved (exchanged) when using that URI with the HTTP protocol. > Even when an authority > does have something to say about a 'http' URI, the authority (should) > make its will known by doing something operational. Examples would be: - Meta-data in header fields? - Making available RDF resource decriptions in some way? - Publishing RSS feeds? Others? > >(from RFC 2396) > > "3.2. Authority Component > > > > Many URI schemes include a top hierarchical element for a naming > > authority, such that the namespace defined by the remainder of the > > URI is governed by that authority. This authority component is > > typically defined by an Internet-based server or a scheme-specific > > registry of naming authorities." > > Perhaps it should be clearer, but the goal of this wording was to define > the generic syntax, and to allow the generic syntax to be used in a wide > variety of schemes. RFC 2396 never mandates that schemes use the generic > syntax, it just makes it available. So I don't think the generic syntax > should ever be taken as _definitional_ for the meaning of URIs. Every > scheme that uses the generic syntax must still say, operationally, how > the components are combined to create semantics. I accept much of this: that RFC 2396 sets up a generic syntax that schemes can opt into. However RFC 2616, appears to opt-in in the specification of the HTTP URI scheme, and albeit the last item in a list, explicitly includes the RFC2396 definition of "authority" (from RFC 2616) 3.2.1 General Syntax URIs in HTTP can be represented in absolute form or relative to some known base URI [11], depending upon the context of their use. The two forms are differentiated by the fact that absolute URIs always begin with a scheme name followed by a colon. For definitive information on URL syntax and semantics, see "Uniform Resource Identifiers (URI): Generic Syntax and Semantics," RFC 2396 [42] (which replaces RFCs 1738 [4] and RFC 1808 [11]). This specification adopts the definitions of "URI-reference", "absoluteURI", "relativeURI", "port", "host","abs_path", "rel_path", and "authority" from that specification. The word 'authority' in the extract from 2396 above is used in two senses. 1) as a syntactic element in a generic syntax; 2) as some instrument of governance over some 'namespace' associate with a value conveyed in such a syntactic element. Is this (over interpretation of the word 'authority' on my part) something that needs to be cleaned-up in the revison of the URI spec.? Regards Stuart --
Received on Tuesday, 30 September 2003 07:03:06 UTC