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Re: [metaDataInURI-31]: Initial draft finding for public review/comment.

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Tue, 15 Jul 2003 11:21:52 +0300
Message-ID: <006501c34aaa$2cdad320$100da20a@NOE.Nokia.com>
To: "ext Williams, Stuart" <skw@hp.com>, <MDaconta@aol.com>
Cc: <www-tag@w3.org>

Stuart,

It seems to me that we are mostly (or even fully) in agreement.

I think it's about where the line is drawn, not whether there is useful
functionality on either side of the line. Thus:

In general, URIs are opaque and agents need not have to peek inside
the URI  to interact with the resource denoted by the URI or discover
things about the resource denoted by the URI.

On the other hand, various URI schemes impose (some more strongly
than others) both structure and semantics on instances of those schemes
which some applications may find regular enough in practice to be useful,
and they then might choose to peek inside the URI  for various reasons.

The key distinction is "NEED NOT" versus "MIGHT".

The "NEED NOT" is part of the general web architecture, and any
application which violates that is in some sense acting contrary to the
fundamental principles of the web.

However, the "MIGHT" may be part of a specialized application
which, by peeking inside the URI may provide additional value to
users of that application, respective to the reliability of the structure
and semantics that might be derived from any URIs.

In the long run, though, I think that peeking inside URIs insofar as
the properties of the denoted resource are concerned, will be risky
and there will be far better ways to obtain reliable, explicit information
about the resource than within the URI denoting it. That leaves URI
structure
and semantics to be optimized for protocol and management issues,
not describing the nature of the thing accessed or managed.

Cheers,

Patrick

--

Patrick Stickler
Nokia, Finland
patrick.stickler@nokia.com



----- Original Message -----
From: "ext Williams, Stuart" <skw@hp.com>
To: <Patrick.Stickler@nokia.com>; "Williams, Stuart" <skw@hp.com>;
<MDaconta@aol.com>
Cc: <www-tag@w3.org>
Sent: 11 July, 2003 19:18
Subject: RE: [metaDataInURI-31]: Initial draft finding for public
review/comment.


> > There is certainly a gray area, in the case where URI schemes
> > impose restrictions on the kinds of resources that should be
> > denoted by instances of those URI schemes. Likewise for any
> > subschemes, etc.
> >
> > That someone would be able to infer an rdf:type assertion
> > based on a URI scheme is logical, and I wouldn't necessarily
> > fault a particular application from doing so.
> >
> > But the number of URI schemes that have such explicit
> > extensions are few, and so it does not seem worthwhile to
> > make such inferences a regular part of the overall web architecture.
> >
> > And since such cases can be addressed just as well by URIQA,
> > why introduce yet another, less general, less flexible, less
> > scalable, and less robust mechanism for publishing knowledge
> > about resources?
>
> I could be quite happy with a 'don't peek inside URIs' position. I am
trying
> to reconcile that with things that other folks seem to want to do... eg.
> make assertions about the nature of things identified by http scheme URIs
> that contain a fragment component. I don't think we can have it both ways.
> The 'middle' ground I was shooting for was allowing ourselves to use
> whatever is stated in the relevant (narrative) specifications. I agree
that
> this doesn't scale. There will be schemes that on manifestly does not know
> about or chooses not to implement - and in such cases the URI are truly
> opaque beyond separating out scheme, hier-part (RFC2396bis), query and
> fragment components.
>
> Regards
>
> Stuart
> --
>
> > -----Original Message-----
> > From: Patrick.Stickler@nokia.com [mailto:Patrick.Stickler@nokia.com]
> > Sent: 10 July 2003 12:42
> > To: skw@hp.com; MDaconta@aol.com
> > Cc: www-tag@w3.org
> > Subject: RE: [metaDataInURI-31]: Initial draft finding for
> > public review/comment.
> >
> >
> >
> > -----Original Message-----
> > From: ext Williams, Stuart [mailto:skw@hp.com]
> > Sent: 09 July, 2003 15:08
> > To: Stickler Patrick (NMP/Tampere); MDaconta@aol.com
> > Cc: www-tag@w3.org
> > Subject: RE: [metaDataInURI-31]: Initial draft finding for
> > public review/comment.
> >
> >
> > For me part of the question is when I (or a piece software I
> > might write) look at a URI (assigned by someone else), what
> > do I allow myself to know (intrinsically from examining the
> > URI rather than going without asking an authority)? (BTW
> > "Nothing" is an acceptable answer). Do I allow myself access
> > to the knowledge embedded in a bunch of normative
> > specifications (and possibly published assignment policies)?
> >
> > At one time, I was a big proponent of "peeking" into URIs to deduce
> > knowledge about the resource denoted, as there did not appear
> > any other reliable, standardized, and globally ubiquitous manner of
> > obtaining fundamental knowledge about resources.
> >
> > You may even recall back a couple of years when I was
> > exploring various means to do this via a more regular and
> > well defined ontology for classifying and relating URI schemes.
> >
> > After a good bit of thought and work, it became evident that
> > a more general solution was needed. And that work lead to URIQA.
> >
> > It is very true that at some stage, an agent is going to have
> > to examine the lexical properties of the URI to apply any
> > protocols or processes defined in terms of the URI scheme,
> > any subscheme, and its structure.
> >
> > But given the function of URIs as identifiers, I am now of
> > the opinion that any knowledge that might be encapsulated in
> > the URI should be justified by the needs of identification,
> > not of description.
> >
> > For description, more open methods such as URIQA which are
> > not limited either by URI structural constraints nor the need
> > (or at least desire) for persistant URIs.
> >
> >
> > Do I allow myself to know that the URI mailto:skw@hp.com
> > identifies an "Internet mailing address", because RFC2396
> > (and successors) allow me to identify a scheme component and
> > RFC2368 as the registered scheme specification for the mailto
> > URI scheme tells me "The mailto URL scheme is used to
> > designate the Internet mailing  address of an individual or
> > service". IMO, if I allow myself to know that
> > mailto:skw@hp.com identifies an "Internet mailing address"
> > then I have 'peeked', allbeit at only the scheme component.
> > Likewise for other URI schemes that state the sort of thing
> > that they are used to identify. Some would say, "No, you
> > don't allow yourselve to know such things... don't peek, URI
> > are opaque (to a web client)." Others want to build rule
> > driven systems that very much depend allowing such
> > inferences... and it was only a little peek... hardly a peek
> > at all... (maybe).
> >
> > There is certainly a gray area, in the case where URI schemes
> > impose restrictions on the kinds of resources that should be
> > denoted by instances of those URI schemes. Likewise for any
> > subschemes, etc.
> >
> > That someone would be able to infer an rdf:type assertion
> > based on a URI scheme is logical, and I wouldn't necessarily
> > fault a particular application from doing so.
> >
> > But the number of URI schemes that have such explicit
> > extensions are few, and so it does not seem worthwhile to
> > make such inferences a regular part of the overall web architecture.
> >
> > And since such cases can be addressed just as well by URIQA,
> > why introduce yet another, less general, less flexible, less
> > scalable, and less robust mechanism for publishing knowledge
> > about resources?
> >
> > Another example, that links with the httpRange-14 debate. One
> > position in that debate is that http scheme URIs without
> > fragment identifiers may only be used to identify network
> > accessible resources, and may not be used to identify
> > abstract concepts (eg. a particular emotion) or a real-world
> > object (like DanC's car or a person) eg. using
> > http://people.example.com/stuart to identify me would be
> > frowned upon.
> >
> > I personally take the opposing view, and find the use of URIs
> > with fragment identifiers to be unwise and problemmatic, and
> > see no reason, technical, philosophical, or practical which
> > would warrant any such restriction from using http: URIs to
> > denote any entity whatsoever that can be named and thus referred to.
> >
> > One of the greatest contributions provided by REST is the
> > abstraction away from "files" or "streams of bytes" allowing
> > URIs to consistently denote a resource (any resource, even
> > Dan C's car) irrespective of
> > whether such resources are bit equal to their representations.
> >
> >  However, within this particular position, it is ok to
> > identify abstract concepts and real world artifacts with http
> > scheme URIs that include a fragment identifier ie.
> > http://people.example.com#stuart would be fine. If we were to
> > accept this particular position, then the presense or absense
> > of a fragment component (even a null fragment) in an http URI
> > allows an inference to be made about whether the referenced
> > resource is a network accessible resource or an abstract
> > concept or real-world thing. Some folks want to build systems
> > that rely on such distinctions... and IMO this again is peeking.
> >
> > I agree. And I would assert that the position that only URIs
> > having fragment identifiers can denote non-digitized
> > resources is (a) already rejected by common
> > usage (b) unnecessarily and IMO unjustifiably restrictive,
> > and (c) unsupported by and contrary to the present definition
> > of HTTP, which requires web clients to omit the fragment ID
> > from requests. After all, if the fragment ID is disposable in
> > a transaction between client and server, how can it be the
> > basis for the semantic web, since the identity of the actual
> > resource denoted by the URIref with fragid is lost?
> >
> > So any inferences that one may presume to derive from the
> > presence or absence of a fragid will be suspect at best, and
> > with the advent of URIQA, unnecessary in any case.
> >
> > "Don't peek inside URI's" is a very simple thing to say and
> > to understand, but I think that even amongst those that might
> > say it there is a temptation to peek - with good reason - so
> > as a prinicple it may be a little to simplistic.
> >
> > I'm not going to take an absolutist view about peeking into
> > URIs. I'm a pretty pragmatic and practical person. It's not a
> > question of recommending "Don't do this" so much as it is a
> > question of  actually recommeding "Do it"  as a general methodology.
> >
> >  Peeking inside URIs will IMO always be plagued with
> > problems, because many/most of the generalities that are
> > percieved in the structure of URIs are not absolute, and
> > hence not reliable.
> >
> > Better to emphasize/promote/optimize methods of publishing
> > and accessing knowledge that is expressed in an explicit
> > manner and governed by a consistent and well defined model theory.
> >
> > Over time, I think, the need for specialized URI schemes will
> > decrease, as will the amount of knowledge packed into URIs in
> > general, as technologies such as URIQA become ubiquitous.
> >
> > Cheers,
> >
> > Patrick
> >
> >
> > Stuart
> > --
> >
> > -----Original Message-----
> > From: Patrick.Stickler@nokia.com [mailto:Patrick.Stickler@nokia.com]
> > Sent: 9 July 2003 10:13
> > To: MDaconta@aol.com; skw@hp.com; www-tag@w3.org
> > Subject: RE: [metaDataInURI-31]: Initial draft finding for
> > public review/comment.
> >
> >
> >
> > -----Original Message-----
> > From: ext MDaconta@aol.com [mailto:MDaconta@aol.com]
> > Sent: 08 July, 2003 21:11
> > To: skw@hp.com; www-tag@w3.org
> > Subject: Re: [metaDataInURI-31]: Initial draft finding for
> > public review/comment.
> >
> >
> > In a message dated 7/8/2003 6:44:46 AM US Mountain Standard
> > Time, skw@hp.com writes:
> >
> >
> > I would appreciate some feedback on this draft. Whether a
> > simpler, shorter, finding is a better path to take? Whether
> > "Don't peek inside URIs" is all that need be said?
> >
> >
> >
> > Hi Stuart,
> >
> > First, to answer your questions:
> > 1. A simpler and shorter finding is only better for the
> > "don't peek inside" position. 2. I disagree with the "Don't
> > peek inside URIs" sentiment.
> >
> > The "Don't peek inside" position stresses the use of
> > identification as an assertion of
> > uniqueness and possibly a mechanism to locate that unique
> > thing.  In essence,
> > an opaque "pointer".  While those are necessary functions of a URI,
> > imbuing an identifier with additional metadata should be
> > encouraged.  First, additional metadata in a URI makes it
> > easier to keep the URI "cool" (as in
> > http://www.w3.org/Provider/Style/URI.html) by > adding
> > classification metadata to the identifier (as with the W3C
> > URLs in your
> > finding).
> >
> > What if the metadata changes? Then you have a different URI,
> > and things break.
> >
> > URIs with metadata embedded in them which might change are
> > hardly "cool".
> >
> > Second, additional metadata in a URI enables a higher-level
> > of efficient processing on resources by applications that *just* want
> > to process URIs.  Opaque URIs would eliminate that increasing
> > possibility.
> >
> > There are better (ie. generalized, scalable, flexible) ways
> > to provide access to resource descriptions than embedding
> > such knowledge in the URIs that denote them.
> >
> > C.f. http://sw.nokia.com/URIQA.html
> >
> > Cheers,
> >
> > Patrick
> >
> >
> > --
> > Patrick Stickler
> > Nokia, Finland
> > patrick.stickler@nokia.com
> >
> >
> > Best wishes,
> >
> > - Mike
> > ---------------------------------------------------
> > Michael C. Daconta
> > Chief Scientist, APG, McDonald Bradley, Inc.
> > www.daconta.net
> >
>
Received on Tuesday, 15 July 2003 04:22:20 GMT

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