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Issue #rdfms-difference-between-ID-and-about

From: Aaron Swartz <aswartz@upclink.com>
Date: Mon, 04 Jun 2001 17:23:36 -0500
To: w3c rdfcore wg <w3c-rdfcore-wg@w3.org>
Message-ID: <B7417497.D20F%aswartz@upclink.com>

    What is the difference between using and ID attribute to 'create' a new
    resource and an about attribute to refer to it?

** What does the spec say? (summary)
[full quotes at the bottom of the email]

 - ID is the anchor id of an "in-line" resource
 - ID signals the creation of a new resource
 - the values of ID must not appear more than once

The spec does NOT say:

 - ID is an XML ID

** The heart of the issue:

 - ID claims to "create" a new resource, but it is assumed by some that
referring to a resource implies its existence.[1]

 - ID claims to define an anchor ID, but it is not defined as an XML ID (and
possibly cannot, because of interaction with bagID[2]) and the editor of the
spec feels that it is not usable as such[3].

 - While ID is in the syntax, it is not specified in the model, which means
that an RDF document cannot be properly "round-tripped" which I feel is an
important goal.

** Proposals

1) Remove/Deprecate ID from the syntax.

   The Working Group could decide to remove ID from the syntax due to
   incompatibility/mistaken compatibility with XML IDs.

   Cons: Breaks backwards compatibility.

2) Allow ID to create triples in the model.

   Sergey Melnik has suggested[4] that ID create an isDefinedBy triple.

   Cons: Requires processors to change their interpretation.

I am willing to hear other proposals, but personally, I currently agree with
proposal 2.

Brian, if available, I would appreciate teleconference time this Friday for
discussion of this issue.

Citations follow:

** What does the spec say? (full)

    The Description element names, in an about attribute, the resource to
    which each of the statements apply. If the resource does not yet exist
    (i.e., does not yet have a resource identifier) then a Description
    element can supply the identifer for the resource using an ID attribute.

(Hmm, a typo: indentifer -- that's one for the errata. ;-))

    The value of the ID attribute of the Description element, if present,
    is the anchor id of this "in-line" resource.

    If another Description or property value needs to refer to the in-line
    resource it will use the value of the ID of that resource in its own
    about attribute. The ID attribute signals the creation of a new resource
    and the about attribute refers to an existing resource; therefore either
    ID or about may be specified on Description but not both together in the
    same element. The values for each ID attribute must not appear in more
    than one ID attribute within a single document.

 - http://www.w3.org/TR/1999/REC-rdf-syntax-19990222

1] http://www.w3.org/DesignIssues/Notation3#Thought
2] http://www.textuality.com/xml/naked
3] http://lists.w3.org/Archives/Public/www-rdf-comments/2000AprJun/0014.html
4] http://lists.w3.org/Archives/Public/www-rdf-interest/1999Nov/0068.html
[ :name "Aaron Swartz" ] is dc:author of <> .
Received on Monday, 4 June 2001 18:24:02 UTC

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