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why S doesn't require double properties [was: Datatyping Summary V4]

From: Dan Connolly <connolly@w3.org>
Date: 04 Feb 2002 11:15:01 -0600
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: RDF core WG <w3c-rdfcore-wg@w3.org>
Message-Id: <1012842902.1760.24.camel@dirk>
On Mon, 2002-02-04 at 07:00, Brian McBride wrote:
> An updated summary of the datatyping issues, as I currently understand them.
> 
> Changes:
> 
>    B1  now disputed
>    B7  status changed to agreed
>    B9  withdrawn
>    B10 added "say what you mean"
> 
> Issue B1:
> =========
> 
> status: disputed by Sergey.  Sergey you owe us an explanation of why.

Perhaps Sergey's position is the same as mine...

> In S, if one wants to use both idiom A and idiom B, e.g.
> 
> <mary> <age> "10" .
> <age> <rdfs:range> <xsd:integer.lex> .
> 
> and
> 
> <mary> <ageD> _:a .
> _:a <xsd:integer.map> "10" .
> 
> two properties have to be used, <age> and <ageD>, in this example.

Yes, *if* one wants to use both idioms, one needs both sorts
of properties.

But I don't think most communities want to use both idioms.
For example, I expect Dublin Core (and maybe prism?) to
recommend S-B exclusively; hence they only need <age>,
not <agedD>.

> I believe there is a agreement that this is a difference between the
> two proposals. Indeed, it may be said that the main aim of TDL is
> to avoid requiring different properties for these different idioms.

[Brian, you asked *why* I hold the position I do; I'm just
about to get on an airplane, so I'm not likely to be able
to phone you as you requested; I don't mind sharing my
motivation with the WG, so...]

Yes, TDL seems to be an attempt to allow folks to use
the name of something (e.g. "10") as that
something (the integer after 9). I know that folks want
to do this; they want to write

	<book> dc:author "Dickens".

and
	<book> dc:author _:x.
	_:x contact:familyName "Dickens".

interchangeably. The bad news is: computers don't handle
this sort of ambiguity the way people do. The TDL proposal
may solve this problem for a privileged few classes
(the XML schema datatypes) but it does not solve
it for people, places, and other sorts of things.
So it's harmfully misleading.



> Issue B5: Storage Requirements
> ===============================
> 
> status: disputed.
> 
> TDL requires significantly more storage to implement.

Sergey got back on this one, no?

In short: you may not need to store the whole string
lots of times, but you do need to store some sort
of distinct identity for each occurence of a string.

[my ride to the airport arrives...]

> 
> 
> Issue B6: S requires 4 URI's be registered for each data type
> =============================================================
> S requires that for each datatype 4 URI's be registered
> datatype
> datatype.lex
> datatype.val
> datatype.map
> 
> Sergey: Do you agree this is the case? If not, how many URI's are required 
> to implement ALL the idioms of S and coexist in the same model.
> 
> 
> Issue B7: Complexity
> ====================
> 
> status: agreed
> 
> S has several ways of expressing the same thing. An RDF processor has to be 
> aware of them all. Supported by Jeremy's error cases message
> 
> http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jan/0397.html
> 
> and a message from Andy Seaborne to rdf comments:
> 
> http://lists.w3.org/Archives/Public/www-rdf-comments/2002JanMar/0058.html
> 
> 
> Issue B8: S-B encourages logically (sic) errors in the
> application type processing.
> =======================================================
> 
> status: ?
> 
> Given:
> 
> _:f <rdf:type> <film> .
> _:f <dc:Title> "10" .
> <mary> <age> "10" .
> 
> an application 'knows' that the range of <age> is an integer so it 'knows' 
> that mary has <age> 10. Under S-B, running a query:
> 
> ?x <dc:Title> ?y .
> ?z <age> ?y .
> 
> will return ?x = _:f and ?z = <mary>, and knowing that the age of <mary> is 
> 10, may conclude that the title of the film is also 10.
> 
> Can't Live With: Jeremy
> 
> 
> Issue B9: In TDL a document does not entail itself
> ==================================================
> 
> status: Withdrawn.
> 
> Under TDL, does:
> 
> <foo> <dc:Title> "W3C" .
> 
> entail
> 
> <foo> <dc:Title> "W3C" .
> 
> yes.
> 
> 
> Issue B10: Say what you mean
> ============================
> 
> status: ?
> 
> The concern here is that in TDL, a literal denotes a pair consisting of a 
> value and a lexical representation of that value.  The problem is then that 
> the german representation of floating point number, e.g. "10,5" is 
> different from the english representation, e.g. "10.5".
> 
> Thus under TDL a german 10 and a half is a different thing from an english 
> 10 and a half.
> 
> 
> More formally, under TDL:
> 
>    <foo>      <eg:size>   _:s1 .
>    _:s1       <rdf:value> "10,5" .
>    _:s1       <rdf:type>  <xsd:double-de> .
> 
>    <bar>      <eg:size>   _:s2 .
>    _:s2       <rdf:value> "10.5" .
>    _:s2       <rdf:type>  <xsd:double> .
> 
> does not entail:
> 
>    <foo> <eg:size> _:s .
>    <bar> <eg:size> _:s .
> 
> Does anyone dispute the facts, or that this is a significant issue?
> 
> 
> 
> 
> 
> 
> 
> 
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Monday, 4 February 2002 12:15:59 EST

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