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Re: DATATYPES: mental dump.

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Mon, 12 Nov 2001 10:00:21 -0800
Message-ID: <3BF00E35.4F666FC3@db.stanford.edu>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
CC: Pat Hayes <phayes@ai.uwf.edu>, RDFCore WG <w3c-rdfcore-wg@w3.org>
Graham Klyne wrote:
> 
> At 08:13 PM 11/9/01 -0800, Sergey Melnik wrote:
> >What do you think (Jeremy, Patrick, Brian, Graham)?
> 
> I agree with much of what you say ... Pat did a great summary.
> 
> I also like your diagram ... I've printed it off and stuck it above my monitor

;)

> My biggest concern is for compatibility with existing use:  as far as I can
> tell, P/P++ are the only approaches that support my perception of existing
> use (and also a form of use that I believe will be helpful in getting XML
> folks to migrate their designs to RDF compatible forms).

This is a very valid concern, I agree.

> Pat said that he
> thought Patrick's approach could support existing use, but I'm not sure how
> that works.
> 
> I think we'll see a lot of RDF usage like this:
> 
>    _:Robby child:age    "12" .
>    _:Robby child:weight "14" .
>    _:Jenny child:age    "12" .
>    _:Jenny child:weight "12" .
> 
> i.e. things like number radix and units will implicit in the vocabulary
> (properties) used.

I believe the above representation could also be utilized in the S
proposal (I think Pat and I are still dashing out this topic on another
thread). In S, the literals "12" and "14" above would represent literal
values, not masses in durations, and child:age would connect directly t2
and s2 in the diagram. However, an application could have a built-in
understanding that

_:Robby child:age "12"

somehow implies

_:Robby IS:age        X
X       IS:inMonth    Y
Y       IS:inDecimal "12"

Given this implicit knowledge, the only valid interpretation for the
IS:age of Robby would be determined uniquely as d1, i.e. "one year". Of
course, in this case the range of child:age would be rdfs:Literal and
not IS:Durations. In other words, if CC/PP uses S, either instances
could be kept "as is", or schema, but not both.

> I can also see that one could have a preferred universal form of measuring
> these things, which is equivalent and can be inferred given sufficient
> knowledge; e.g.
> 
>    _:Robby SI:age    [ a SI:Duration ; rdf:value "32140800" ] ;
>            SI:weight [ a SI:Mass ; rdf:value "14" ] .
> 
>    _:Jenny SI:age    [ a SI:Duration ; rdf:value "32140800" ] ;
>            SI:weight [ a SI:Mass ; rdf:value "12" ] .

This would also work. However, great care is advised to ensure that
exactly one rdf:value can be attached to a given entity in the
interpretation. Otherwise, conflicts like the one illustrated in
http://WWW-DB.Stanford.EDU/~melnik/rdf/datatyping/fig/units1.gif may
arise.

Sergey


> 
> #g
> --
> 
> At 08:13 PM 11/9/01 -0800, Sergey Melnik wrote:
> >Pat,
> >
> >thanks for a great "dump". I'm going to work it into the document almost
> >completely, if you don't mind.
> >
> >I'm thinking of a running example that can be used to illustrate the
> >different proposals and modeling options. My current shot at it is:
> >
> >http://WWW-DB.Stanford.EDU/~melnik/rdf/datatyping/fig/motivating_example.gif
> >
> >It shows an interpretation, which can be encoded in many different ways,
> >e.g. as:
> >
> >_Robby ageMonthDecimal "12"
> >_Robby weightKgDecimal "14"
> >_Jenny weightKgOctal   "14"
> >_Jenny ageYearsDecimal "1"
> >
> >in P(++) scheme.
> >
> >The advantage of starting with an interpretation instead of a piece of
> >syntax is that is it possible to refer to the different entities in the
> >domain of discourse directly and tell how the corresponding pieces of
> >syntax are mapped onto them (for example, "12" and "1" above are
> >interpreted as entity d1 in the figure).
> >
> >What do you think (Jeremy, Patrick, Brian, Graham)?
> >
> >Sergey
> 
> ------------------------------------------------------------
> Graham Klyne                    MIMEsweeper Group
> Strategic Research              <http://www.mimesweeper.com>
> <Graham.Klyne@MIMEsweeper.com>
> ------------------------------------------------------------
Received on Monday, 12 November 2001 12:33:15 EST

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