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Re: Some comments on 27 June 2003 Web Arch WD

From: Ian B. Jacobs <ij@w3.org>
Date: 14 Jul 2003 11:26:42 -0700
To: David Orchard <dorchard@bea.com>
Cc: www-tag@w3.org
Message-Id: <1058207202.903.113.camel@seabright>

On Thu, 2003-07-10 at 16:26, David Orchard wrote:
> - "On the web" is not defined in this document.  I would think that we would
> want to define what "on the web" means for V1 of the Web architecture.  My
> stab <shields mode="up">"On the Web means that a URI may be dereferenced
> without the input of a representation, typically a GET retrieval.  Being on
> the Web versus not on the Web is a trade-off in properties achieved and is
> not be default a "bad" thing.  Some Web resources necessarily must be off
> the Web, such as HTML FORM POST results." </shields>

[Being discussed elsewhere.]

> Section 3. Representation
> 
> This section should contain a definition of a "message", and explain the
> relationship between message, representation, representation metadata, and
> other metadata.  "message" is mentioned in bullet 2.
> 
> I believe the last sentence in the 2nd bullet is slightly incorrect.  "When
> transferred by a Web protocol, a representation often includes metadata
> about both the representation and the message bearing the representation
> (for example, some HTTP headers). "
> ->
> "When transferred by a Web protocol, a message often includes metadata about
> any contained representation and the message itself (for example, some HTTP
> headers). ".
> 
> representations don't include message metadata, the messages include the
> message metadata.

I think the TAG intentionally defined representation to include
both types of metadata; see below.

> A diagram would be really good for this, ie:
> Message is:
> +----------------+
> |+--------------+|
> ||metadata      ||
> |+--------------+|
> |+--------------+|
> ||representation||
> |+--------------+|
> +----------------+

We discussed this at the Feb ftf meeting in Irvine
http://www.w3.org/2003/02/06-tag-summary#archdoc-cl

Though there was no formal resolution from that discussion,
but you raised a similar point at that time. I believe the
end of the discussion was to define representation to
be data + metadata. The metadata included both the metadata
about the data and the metadata about the message. In particular,
Roy said:

   "RF: Representation defined this way so that it has the same meaning 
    in both PUT and POST situations. You don't create messages on a 
    server; you create representations."

Roy also said:

    "RF: We know that that it was a mistake in HTTP to not be able to 
    distinguish msg metadata from representation data. We would fix that
in the next protocol spec."

I take this as a proposal to reopen the definition of representation
as I understood the TAG had decided it at the ftf meeting.

> 3.3.2
> "Authors and applications can use URIs uniformly to identify different
> resources on the Web" -> "Authors and applications can use URIs uniformly to
> identify different resources".

Ok.

> 
> 3.3.3
> "The simplest way to achieve this is for the namespace name to be an HTTP
> URI which may be dereferenced to access this material. The resource
> identified by such a URI is called a "namespace document."  ->
> "The simplest way to achieve this is to provide a resource, called a
> "namespace document", that is identified by a dereferencable URI."

[In discussion elsewhere.]

-- 
Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Monday, 14 July 2003 15:22:06 GMT

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