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Re: rdfms-not-id-and-resource-attr

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Thu, 03 Jan 2002 11:32:36 +0000
Message-Id: <5.1.0.14.2.20020103112020.03963cd0@joy.songbird.com>
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: <w3c-rdfcore-wg@w3.org>
I think I agree with all Jeremy is saying here.  In particular:

>I find two possibilities acceptable:
>+ dropping reification in its entirity
>+ having a plausible syntax for reification

I'm unsure which way I actually prefer at this point.

[...]

Where a "plausible syntax might be:

>I propose that we
>+  decide that rdf:ID on property elements productions uniformly
>    signals reification
>+  action the syntax WD editor to make the necessary changes

..

On reflection, maybe there is a third possible way?  A syntactic variation 
of reification (e.g. rdf:reifyAs='...') that:
(a) does not add the statement triple to the graph, but
(b) adds the reification quad describing the statement to the graph, using 
the given identifier to label the statement node.

I think this achieves a key goal of reification, namely use without 
assertion, without being forced to code all the reification quads.

As this is out of scope for our current charter, it suggests to me that 
reification by rdf:ID be dropped for now, and (if desired) reconsidered for 
a future revision of the specification.  However, I think it is still worth 
defining the reification vocabulary, without special semantics, so there is 
some common basis for experimentation and future development.

#g
--

At 04:53 PM 12/16/01 +0100, Jeremy Carroll wrote:
>It was proposed at the Dec 14 telecon that the current syntax
>working draft resolved the issue:
>
>  http://www.w3.org/2000/03/rdf-tracking/#rdfms-not-id-and-resource-attr
>
>
>It was noted that agreeing to publish the working draft *does
>not* implicitly agree this.
>
>I oppose this proposed resolution.
>I currently intend to vote against it at the next telecon.
>
>I find two possibilities acceptable:
>+ dropping reification in its entirity
>+ having a plausible syntax for reification
>
>I am concerned about the proposed meaning of the rdf:ID attribute
>in certain empty property element productions (those with one or more
>propertyAttr).
>http://ilrt.org/discovery/2001/07/rdf-syntax-grammar/#emptyPropertyElt
>
>   gives rdf:ID in this case the meaning of identifying the object node of
>the property element triple.
>
>In all other cases, an rdf:ID on a propertyElt identifies the reification of
>the property element triple.
>
>The phrase "property element triple" above means the triple created as a
>result of the property element with predicate given from the qname of the
>property element start tag.
>
>
>As I have previously argued M&S is inconsistent and has been
>inconsistenly implemented and can be clarified in a number of
>different ways. Dave's clarification has the side effect of
>being to continue to apply the death of a thousand cuts to
>reification.
>
>Dave's position is that in the document:
>
><rdf:RDF xmlns:rdf="..."
>          xmlns:x="http://example.org/">
>   <rdf:Description>
>      <x:prop rdf:ID="r1">val</x:prop>
>      <x:prop rdf:ID="r2" rdf:parseType="Resource">
>          <x:prop>val2</x:prop>
>      </x:prop>
>      <x:prop rdf:ID="r3" rdf:parseType="Resource"/>
>      <x:prop rdf:ID="r4"/>
>      <x:prop rdf:ID="x5" x:prop="val2" />
>
>   </rdf:Description>
></rdf:RDF>
>
>
>That the property attribute rdf:ID within a property element
>maps to reification in the graph for almost always (e.g. cases
>r1, r2, r3, r4) and just occassionally, according to some baroque
>rules that are still incorrectly articulated, it has some other
>semantics. (See following posting for feedback on the mistake - this of
>course can be fixed, but is symptomatic of a bad rule).
>
>The result is that anyone who isn't an RDF syntax expert cannot use
>reification, because every so often this corner case will come back
>and bite them.
>
>If that is what we want, we should kill reification completely.
>
>
>Hence,
>
>given that:
>-  M&S gives two inconsistent readings for the relevant productions
>-  implementations have varied in their misreadings of M&S on this issue
>-  it was raised very early in RDF comments that M&S is inconsistent
>   (and this comment has not yet been satisfactorily addressed)
>
>
>I propose that we
>+  decide that rdf:ID on property elements productions uniformly
>    signals reification
>+  action the syntax WD editor to make the necessary changes
>
>
>Moreover, but independently,
>
>I propose that we allow rdf:ID and rdf:resource on empty property
>element productions.
>
>(This is a change, but seems to me to be only a simple tidying up.
>If no one else agrees with this last point, I would not oppose
>the opposite resolution).
>
>
>Links:
>   A previous thread:
>http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Oct/thread.html#332
>   The first posting to rdf comments on this issue:
>http://lists.w3.org/Archives/Public/www-rdf-comments/1999JanMar/0026.html
>
>On killing reification:
>
>That is a serious suggestion, I have prepared a proposal to that
>effect but I am seeking feedback from HP colleagues before making it.
>i.e. as HP rep, I should try to check whether any HP people use, or
>intend to use, reification before finalising my position on it.
>(It would be kind of embarrassing if I had to oppose my own proposal because
>my colleagues felt strongly the other way!).,
>
>
>Jeremy

------------------------------------------------------------
Graham Klyne                    MIMEsweeper Group
Strategic Research              <http://www.mimesweeper.com>
<Graham.Klyne@MIMEsweeper.com>
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Received on Thursday, 3 January 2002 08:21:39 EST

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