W3C home > Mailing lists > Public > www-tag@w3.org > July 2009

RE: LRDD Update (Resource Descriptor Discovery) and Proposed Changes

From: Williams, Stuart (HP Labs, Bristol) <skw@hp.com>
Date: Thu, 2 Jul 2009 13:03:02 +0000
To: Xiaoshu Wang <wangxiao@musc.edu>
CC: Jonathan Rees <jar@creativecommons.org>, "www-tag@w3.org" <www-tag@w3.org>
Message-ID: <233101CD2D78D64E8C6691E90030E5C832D33A5AE6@GVW1120EXC.americas.hpqcorp.net>

> -----Original Message-----
> From: Xiaoshu Wang [mailto:wangxiao@musc.edu]
> Sent: 01 July 2009 16:39


> Williams, Stuart (HP Labs, Bristol) wrote:
> > Xiashou,
> >
> >> -----Original Message-----
> >> From: Xiaoshu Wang [mailto:wangxiao@musc.edu]
> >> Sent: 01 July 2009 13:52
> >>
> >
> > <snip/>
> >
> >>>> Then, this comes back to the definition of Information Resource, with a
> >>>> URN, wouldn't IR be the set of all URL's referent?
> >>>>
> >>>>
> >>> By Fieldings writings a resource is modelled as a function from time to
> >>> [(sets of equivalent awww:representations) OR (URI)].
> >>>
> >>>
> >> By no means to disrespect Fieldings, do we have to take someone's past
> >> writing as a bible that we should never change?  If that, how can we
> >> ever advance?
> >>
> >
> > You propose IR as ".. The set of all URL's referents". This
> > makes no sense to me. In your view are those referent things
> > resources or representations - it is not clear from what you write.
> >
> > I invoke the model written about in REST and I think mostly
> accepted in the community... which I happen to like and find
> it makes sense to me.
> >
> > You take umbrage...
> >
> Nope.  I did not.  My wording my imply that I suggested Fielding's model
> is wrong.  This is not the case.  I am simply questioning the approach
> that you are using.  What Fielding has done is simply explain what is
> working.  It is not the reverse that the Web runs because of his
> interpretation.  What I am doing is just the same.  I am trying to find
> an interpretation that gives me a peace of mind and makes my daily job
> easier.

Fair enough...


> >> That is my view, there is no "information resource".
> >>
> >
> > Information resources are just those that can have webarch repesentations...
> >
> Please, please, define the "can"!  Whose capability?  I told you that "I" can give any awww:representation to any resource.
> And 200 signals *my* capability.  But I cannot speak for anyone-else or anything-else.  Who or what gives the awww:representation
> of a web-page?  Is it the web page itself that gives it a awww:representation? Or you, or I, he or she?

FWIW: (as I have said before) I think of the web as a big machine that produces awww:representations of things (named by URI) when asked 'get' questions. I tend to think of it as the web itself 'inspecting' the resource hand delivering up a awww-representation *of* it. Others may think of it differently (and there may be other agency in the production of awww:representations) - but it is a way of thinking that satisfies me.

I do not believe that it is possible for there to be an awww:representation of me, or indeed of anything else with non-zero mass.

Jonathan gave you a fuller response about crispness (or lack thereof) in the definition of information resources [1] (starting at his 5th para).

[1] http://lists.w3.org/Archives/Public/www-tag/2009Jun/0176

> I do *not* think that a web-page can have an awww:representation by
> itself.  Then, I can only 303 forever.
> >>> The point is that in web architecture the 'thing' referred
> >>>
> >> to by the 'uri' in the question, and the 'thing' that the
> >> awww:representation (if any) is an awww:representation of are
> >> supposed to be the *same* 'thing'.
> >>
> >>>
> >>>
> >> You have repeatedly assured me that no one has taken the view of
> >> "Resource = Representation".
> >>
> >
> > Yes... no-one I know of on the TAG... and I would continue
> to assure you of that...
> >
> >
> >>  What was this supposed *sameness*?  Define it objectively
> and clearly.
> >>
> >
> > I think I'd refer you earlier responses from Pat or
> Jonathan about the meaning of sameness.
> >
> > Best I can do is:
> >
> > ForAll ?u:uri ?r:wa-representation SuchThat
> http-get(?u:uri) yields ?r:wa-representation,
> > Exists ?t:thing SuchThat
> >     ?u:uri refers-to ?t:thing,
> >     ?r:wa-representation wa-representationOf ?t:thing .
> >
> > Thing ?t is the same thing t in both clauses that m. That's it!
> >
> Then, what criteria to evaluate "wa-representationOf"?

I don't think I can help you much further! (or maybe vice-versa :-) ).

> Please, you think it says anything?  Just like in a programming language, the
> language itself has an object identity equivalence, same as the
> equivalence of URI comparison by char by char.  All other semantic
> equivalence is delegated to the programmers.  What is did in
> that is to simply delegate it to the Web user to implement the
> "wa-representationOf".  There is no definition.

One view (which is what tried to say above) that it is axiomatic that the awww:representation returned (if any) is an  awww:represention of the resource reference.

Now you might choose to say that http://wwww.example.net/people/skw is a URI that names me, and somehow arrange for an awww:representation identical to at http://farm1.static.flickr.com/139/330868183_7b18c0ce4c_b.jpg to be served from that URI.

I would find that inconsistent - the claim that the URI named me and that the served representation was of an image that depicted me. I would feel that the URI (at least at that point in time :-) ) named a particular image.

[BTW: I can live with the other model where representations of things may be descriptive/depictive of them (Jonathan's 'X' model) - but I a choosing to try to work within other model - Jonathan's 'T' model]


> > Oh well... good luck... I suppose! I think you'd actually
> have more success in proposing a new scheme that fits with
> URI architecture as it is (and BTW URI schemes (as they are
> now) are orthogonal to fragID syntax/semantics). Not that
> would be without significant impedance.
> >
> I am asking TAG to consider.  Sure, we could built a schemeless or other
> named URN. That really doesn't matter to me.  What I want is first, to
> make people aware of the two sense of a HTTP-URI that is currently
> used.  So people won't try to make a quibble by using tricks in natural
> languages.   For instance, I have to stop Jonathan's earlier example
> time and time again, just wanting him to be clear which thing, i.e., a
> representation/referent that his use of "web page" is referring to.
> Otherwise, there is no way the argument can proceed.

I think that you'll find Jonathan in using the word 'document' or 'web-page' is referring to a resource (a referent as you pose the question).

> Second, we need *syntactic* difference to denote the concept that we
> used quite often.

Difference betweeen what?

I'm being picky here because "the concept that we used quite often" is a vague reference to something - but I don't know precisely what.

> It is a matter of convenience. For instance, we do
> not have to invent the word "red" to mean a particular kind of color.
> We can just do it by how it relate to other colors.  But we do it in
> life because it makes our life easier.  Providing a syntactic construct
> just forces a certain clarity.  You can consider it to be too rigid.
> But so does the grammar in a natural language.  The purpose is to ensure
> the clarity of language use.
> >>> Also, whilst I think this is the topic of TAG issue
> >>>
> >> schemeProtocol-49, what a URI refers to and how you access
> >> that 'thing' (if you can) should be regarded as orthogonal.
> >> The HTTP protocol itself can be used with URI from any scheme
> >> - though there are obvious practicalities in setting up the
> >> relevant gateways/proxies.
> >>
> >>>
> >>>
> >> Wouldn't my proposal help clarify that? A scheme denotes a path to
> >> acquire "awww:representation" of a resource, denoted by the
> >> schemeless-URI? If we give a default namespace to the scheme
> >> part.
> >>
> >
> > *But* that is what the web already is - a machine that obtains wa-representions (where possible) of things
> > (resources) designated by URIs.
> >
> >> Then, people can follow their nose to understand what is the protocol, right?
> >> If you take a static view point, then what a schemed URI denotes is the
> >> "information resource". Besides, it also solve the problem between the
> >> equivalence of http-URI and https-URI.
> >>
> >
> > Hmmm... you may think you have solved it others with
> > deployed systems that depend on the fact that such an
> > equivalence is not stipulated probably see neither a problem
> > or a solution!
> >
> Honestly, as a person, I couldn't careless because I, as a web engineer,
> know the intrinsic relation between an HTTP and HTTPS URI.

In general there is none... I hope that that is what you mean. It may be the case that there is some intrinsic relation for the ones that you define... but that is less than universal in scope.

> But handling that job to an RDF reasoner and see where kind of problem it
> may give rise?
> >> I am not saying this is currently supported.  That is why I ask TAG to
> >> consider. We do use URI in two senses, one as URN and the other URL. Do
> >> you agree?
> >>
> >
> > As a name and as a locator... Yes I see those uses, but the
> > intention of webarchitecture AIUI is that in those case where
> > both usages are possible they are (should be) aligned - what
> > is named is that which is located (ie. that which an obtained
> > representation is a representation *of*).
> >
> We go back to full circle.

As we so often do... maybe we should simply agree to disagree and (both) stop... ("yes please" say the observers that we've plagued with this thread).

> I think anything can be *of* anything-else.
> If you think otherwise, define your "of"-ness.
> I cannot help pleading Wittgenstein's principle -- "Meaning is use."  If
> you think that a term will affect people's engineering practice.  Then,
> please *define* it with objectivity and clarity.
> If we really want the web architecture to be pragmatic, as Jonathan has
> said before, I really hope that we can understand how Wittgenstein has
> changed philosophy.  Let's *please* not use these all purpose term to
> convey our criteria because it can be used in all purpose to either
> support or against our criteria.  Let's *please* define pragmatic terms
> so we will not be trapped by our linguistic ambiguity.


> >> You want to propose an http://ftp://http://... .
> >>
> >
> > No!!! I am asking you what you would propose. I'd leave things as they are!
> >
> Then that is what I propose, if we want to make the syntax of URI
> syntactically complete.  Say if you are given a URI in the form of
> "http://http://URN".  Then, from the default scheme URI, say
> "http://example.com/scheme/http", where you will find that currently
> HTTP protocol only supports one level of scheme-recursion. Meaning: the
> thing still exists (if you ask the meaning of this letter word, I will
> refer you to Quine) but currently there is no implementation.  That is,
> you cannot write a *page* about it.  Please note, the *page* that you
> are referring, w.r. to http://URN, is not the same kind of *page* w.r.
> to URN.  If you only want to write the-web page but not the meta-web
> page, you write it in say: http://URN2, where you make an assertion to
> say "URN2 = http://URN1".  Isn't it right and clear?

I have no idea... I cannot make sense of what you are proposing or how it would make life better for you.

> >> Sure.  I don't think
> >> my proposal is theoretically against that. ou have to define how the
> >> inner scheme is grounded on.   In other words, you have to construct a
> >> meta-Web to do that.  But do you think that it is practically useful?  I
> >> think Godel has told us there is no system that can be self-complete. We
> >> have to stop our recursion somewhere.  Otherwise, we will go nowhere.
> >>
> >>> I don't think that we need such rigidity. We just need to
> >>> be careful about what it is that is being named, and some
> >>> named things contain information about other named things.
> >>>
> >>>
> >> Sure.  I am all for that.  Then, think about IR/httpRange-14, is it
> >> rigid or not?
> >>
> >
> > It is very flexible - it does not lock in any rigid
> > syntactic relationship between things whose names have
> > similar but slightly different names. Descriptive information
> > about a thing could be anywhere on the web.
> >
> Really?  Flexible to whom?  Then, why you said that I cannot 200 back
> http://example.com/aperson, which denote a person????

It is flexible because it doesn't build semantic relationships into the syntax of URI as you appear to be proposing. There is no required syntactic relationship between the names of things and the names of things about those things...

Well if you want to give me back a 200 response your challenge would be to provide an awww:representation of that person. I would maintain that no such thing exists, so any awww:representation you fed me was necessarily an awww:representation of something else (most likely of a depicition or a description of that person).


> >> Did I?  I am not against people using the word "meta-data".  I am
> >> against people trying to propose a standard approach based on that
> >> word.  I don't care what the word is.  What I care is how I can tell one
> >> thing from the other.  I am engineers.
> >
> > Ok... so the engineering problem is:
> >
> >     "Given a name 'u' for a thing 't' how do I find descriptions of 't' as opposed to awww:representations of 't'"
> >
> I got lost.  Dereference U, what-else?

Well, Jonathan would likely offer an example of obtaing bibliographic data *about* a publication, and for the sake of it lets say that the publication has only a text/plain representation and doesn't carry information about the author, date of publication etc within the content of the document.

> Or you mean find t's description without getting any t's representation?

Yes... Jonthan would like note that he'd like the option to do that for any kind of resource, not just those that don't happen to have awww:representations.

> Then, should I say more?

?? I have no idea.

> >> All works is in essence a bunch
> >> of "if elese".  If my "if" always return one result, what is the
> >> "else"?
> >>
> >
> > skw parser failure!
> >
> >
> >> And someone told me that there is an "else".
> >>
> >> (As a history, I remember when I first heard RDF back in 2000, it was
> >> called a metadata framework.  I guess there is a reason for
> >> that TAG no longer use that.)
> >>
> >
> > I doubt it.
> Seriously?  See the 1999 version of RDF at
> http://www.w3.org/TR/1999/PR-rdf-schema-19990303/.

What I doubted was "I guess there is a reason for that TAG no longer use that."

> > There is also a 'D' in the middle of RDF. RDF lets you make
> > statement about 'things', but one of the problems is
> > completely the reverse - I want to find what is said (and by
> > whom) about some 'thing'.
>  From where?  From the Web, you (1) dereference it or (2) google/yahoo/bing etc.
> > The natural operation of the web enable you find what a 'thing' has to say of 'itself' in the form of
> > awww:representations (if of course it is of a kind that can do that).
> >
> I am not sure what it has to do with the LRDD proposal?  What LRDD
> recommends is: in addition to wrap your information into the
> HTTP-entity, you need to make two wraps -- one descriptive/metadata and
> the other (non-)descriptive/data -- and place the former in LINK while
> the latter in Entity.  I told them now I have trouble making two
> separate wraps.  I want them to be clear on what I should put in the
> Link bucket and what Entity? I am perhaps the numbest people in the
> world.  But so far, no one has been able to demonstrate his
> or her acute sense to me yet.

AIUI... *if* you want to make available some information *about* some resource - LRDD suggest mechanism that enable you to do so and for other s to reliably find it. You don't have to use any of them; you don't have to do all of them. In some cases you can be intrusive on resource representation - in others you cannot (media-type limitations, curation policies...).

> Xiaoshu

Received on Thursday, 2 July 2009 13:04:36 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:33:02 UTC