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Summary of comments about webarch

From: Ian B. Jacobs <ij@w3.org>
Date: Fri, 20 Sep 2002 12:53:03 -0400
Message-ID: <3D8B526F.1010100@w3.org>
To: connolly@w3.org
Cc: www-archive@w3.org, ij@w3.org, Stuart Williams <skw@btinternet.com>


  [[[1. DC to summarize comments on arch document as input to f2f]]]

    -- www-tag@w3.org from September 2002: [Minutes] 09 Sep 2002 TAG
    Wed, 11 Sep 2002 19:48:15 GMT

I've gone ahead and done this in preparation for the ftf
meeting [2]. Below is a summary of comments on architecture document:

  - Ian

[2] http://www.w3.org/2002/09/24-tag-agenda

General comments (other than editorial)

Comments from Roy pre-publication:

   "So, given a desired set of properties, how do want to
   constrain the interaction between elements such that the
   desired properties are obtained?  That should be the focus of
   our architecture document."

  - Definitions of architecture, principle, agent
  - Description of REST out of place

1 Introduction

 From Joseph Reagle:

   "Is RDF rightfully considered a format? I think of it as a
   data-model that can be expressed in the XML format. (The use of
   "data format" to describe an application probably is correct,
   but counter to my intuition.)"

To which Graham Klyne replies:

   "I think yes, to the extent that the RDF specs do normatively
   define an XML-based serialization format for the RDF data model.
   Being close to the different facets of RDF, I tend to use the term
   RDF/XML to describe this format, but I think it's reasonable for a
   wider audience to expect the term RDF to presume its XML

 From Elliotte Rusty Harold (re Protocols):

   "I am not sure SMTP properly belongs here ..."

   "...Consequently, I am suspicious that principles designed for
   good HTTP/ FTP/etc.  may be actively harmful to good SMTP (and
   vice versa). I do not think this document should attempt to
   prescribe architecture for SMTP in particular or e-mail in
   general. It's just too different."

 From Bill de Hora:

   "Perhaps the document should be more specific as to what it
   means by obligation, or perhaps the link to the qualifying
   document is enough."

 From Mark Baker:

   "Just to be clear, because I think the draft is, SMTP is said
   to be included as part of the Web, not of Web architecture per

   "IMO, a litmus test about whether another system could be
   counted as part of the Web would be;

    a) are the operations of this system performed on things with
    identity (i.e. can they be URI-ized)?

    b) could an HTTP gateway be constructed which mapped the
    application interface of this system to HTTP's application
    interface (perhaps extended), while preserving enough of the
    other system's functionality to be useful?

   In my definition, a) is necessary and sufficient for a system to be
   counted as part of the Web."

2 Identifiers and resources

Anthony Coates

Regarding editor's note:

   "I would venture that a URI identifies a resource, but that a
   complex resource might contain portions that people equate with
   individual "things" or "concepts".  In that view, the resource
   would be a compound resource."

But Paul Prescod asserts:

   "But the XPointer specification disagrees with you."

Anthony replies:

   "Well, it is really the W3C XML Schema Datatypes document that
   says this, not just l'il ol' me."

Meanwhile, Reagle writes:

   "I don't know what the exact answer to the latter part of the
   paragraph is, but xmldsig/xenc certainly uses frag-id's as part
   of the identifier..."

Dan Connolly

   "absolute URI reference" considered awkward (and in one case,
   overly constraining)"

   Regarding" "When one resource refers to another via an absolute
   URI reference, a link is formed."

   Proposal: "I think the simplest fix is to s/absolute//."

Tim Berners-Lee replies:

  "It is important to distinguish between the string which
  identifies something and the BNF for a string in a document
  which is used to specify the first string.  The first is an
  identifier.  The second has been called a "reference".  A
  reference can use a relative form."


    What: The actual identifier in general, with or without #fragid
    Old:  Absolute URI Reference
    New:  URI

    What: A reference to the above
    Old:  URI Reference
    New:  URI Reference

    What: An identifier with no "#"
    Old:  URI
    New:   <need to make something up maybe>
          [Mark Baker: Network URI]

  But what of inconsistency with the RFC?

  From Larry Masinter (defining 'URI'):

   "When we update RFC 2396, I suggest we add an introductory
   paragraph explaining that the term "URI" is used ambiguously in
   the community to mean "a URI reference" (corresponding to the
   URI-reference BNF entity) or "an absolute URI", and that for
   this reason, the term "URI" itself is not defined in the

   "I think "redefining the term URI to mean something precise" is
   one of those "boiling the ocean" tasks: lots of energy and it
   won't work anyway. Why waste energy on this? If you need a
   technically precise term, use something whose meaning hasn't
   been blurred (e.g., 'anyURI' in the XML schema spec means
   something precise)."

  Summary from Stuart Williams (regarding scope of URI references):

2.1 Resources, URIs, and the shared information space

 From Reagle:

   Regarding: "Use absolute URI references: All important
   resources SHOULD be identified by an absolute URI reference."

   'What exceptions are permitted? Is this to accommodate the use
   of QNames as identifiers? (Can one have an identifier without a

To which TBL replies:

  "This is an example of the confusion between the identifier and
  a reference.  This confusion is really exacerbated by this awful
  term "absolute URI reference" for the identifier!  A QName is a
  perfectly good reference to something which is identified by a
  URI.  The QName isn't itself a URI, just as a relative reference
  a not a URI."

Reagle responds:

  "Ah, this makes a lot of sense to me when you put it that
  way. But it's not exactly what the TAG finding says..."

Norm Walsh follows up:

   "Absent a mapping from foo:bar to an absolute URI reference, we
   can't say what URI identifies foo:bar.

   "Until rdfmsQnameUriMapping-6 is resolved, I'm not sure I can
   agree wholeheartedly with the assertion that qnames are
   references to things identified by a URI. I fear that
   URIEquivalence-15 will have some bearing as well (though
   perhaps not)."

2.2.1 Comparison of identifiers

 From Dan Connolly:

   "It's perhaps not an aside, but rather an important feature of
   Web Architecture that each of us can pretend that there's One
   Web... the fact that the intranet guy can't dereference my
   postscript file is in some formal/technical sense an error or
   anomaly, but in practice, it doesn't cost either of us any
   trouble at all."

2.2.2  Interactions with resources

 From Elliotte Rusty Harold (regarding principle 4 and micropayments)

   " I am worried that this precludes the eventual development of
   micropayments; in particular pay for page models. Although as
   yet theoretical, one of the explicit goals of micropayments is
   to make the cost low enough that the user does not need to
   decide whether to pay for each song/article/stock
   quote/picture/movie etc...."

Tim Bray replies:

   "I do *not* want to make payments, even micropayments, as a
   result of doing a GET, without have done an explicit prior
   authorization.  Obviously some sort of distributed
   authorization framework is interesting so you don't have to do
   it separately with every site, but at the end of the day I
   think principle #4 holds up.

   Hmm.. perhaps a re-write along the lines of not incurring *new*
   obligations or some such.  Or not "make a commitment" or some

More from Noah Mendelsohn (concurring with Mark Baker, suggesting
   an additional example).

  "If we can't distinguish an access that incurs obligations from
  one that does not, I fear that no access can be viewed as
  completely safe. "

2.2.4. Absolute URI references and context-sensitivity

 From Reagle:

    'Each absolute URI reference unambiguously identifies one
    resource, but the resource itself may be defined in a
    context-sensitive manner.'

   "Is the actual language (e.g., content negotiation) considered
   a different representation of the same resource?"

2.4 URI Schemes

Danny Ayers

   "I suggest a change in the wording to "Unregistered URI schemes
   SHOULD NOT be used on the public Internet"."

 From Reagle:

   "I'd move this box below the following paragraph, "The IANA"
   because what it means to be a registered or unregegistered
   media type is not yet defined."

2.5 Fragment identifiers

Chris Lilley: Replacement text re: circle or spline

Support from Tim Bray, and Graham Klyne
Disagreement from DanC:

Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Friday, 20 September 2002 14:12:00 UTC

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