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Re: Tidy/untidy: that's all about assumptions, folks

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Thu, 26 Sep 2002 10:34:41 +0200
Message-ID: <3D92C6A1.6040301@db.stanford.edu>
To: Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
CC: RDF Core <w3c-rdfcore-wg@w3.org>

Jos De_Roo wrote:

> Sergey, what are you saying?
> I mean I already follow that you said like
> 
> :Maaike :age "45" .    #about my wife
> :Jos :shoeSize "45" .
> 
> entails
> 
> _:x :age _:z .
> _:y :shoeSize _:z .
> 
> which I wholeheartedly agree with
> but what is that "critical assumption"
> that you talk about?


The assumption is that the values of age and shoeSize properties have to 
denote "ages" and "shoe sizes", and so the above entailment is "wrong". 
This assumption must not hold. The property values may just as well be 
strings/integers/etc. and we still get a coherent model-theoretic 
picture, in which the above entailment is just fine.

> I can think that a statement should
> "restrict the intepretation" and that
> it can use self-identifiers for that
> (but that's again my tidy side)


That's what I meant, too.

Sergey

 
> -- ,
> Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
> 
> 
>                                                                                                                                         
>                       Sergey Melnik                                                                                                     
>                       <melnik@db.stanfor        To:       RDF Core <w3c-rdfcore-wg@w3.org>                                              
>                       d.edu>                    cc:                                                                                     
>                       Sent by:                  Subject:  Tidy/untidy: that's all about assumptions, folks                              
>                       w3c-rdfcore-wg-req                                                                                                
>                       uest@w3.org                                                                                                       
>                                                                                                                                         
>                                                                                                                                         
>                       2002-09-25 07:00                                                                                                  
>                       PM                                                                                                                
>                                                                                                                                         
>                                                                                                                                         
> 
> 
> 
> 
> 
> In the heat of our argument about tidiness, we seem to be forgetting
> about a critical assumption that was suggested to justify untidy
> literals. Below, I'm questioning this assumption. If it holds, than
> untidy literals are a natural decision to make (and I voted for it last
> time), if it does not, there is no sufficient justification for
> introducing untidiness. What I'm arguing for is that we simply have to
> remove the prism we've been looking through recently, and untidiness
> goes away.
> 
> Recall the motivating example from the RDF 1.0 Spec:
> 
> foo dc:Creator "John Smith"
> 
> Is "John Smith" supposed to represent a person or a string? The key
> argument behind untidiness is that "John Smith" (or "10") cannot
> possibly be meant to be a string, so it has to be something else, whose
> meaning can be deduced using a right bit of logic and AI.
> 
> Or, consider our beaten up
> 
> :x age "10"
> :y shoeSize "10"
> 
> Again, the claim of proponents of untidiness is that "10" cannot
> possibly be meant to denote a string, in both cases. Why? Because we can
> infer
> 
> :x age :z
> :y shoeSize :z
> 
> supposedly meaning that the age of :x is the shoeSize of :y. Ok, we have
> datatyping now, so let's do it right:
> 
> :x age int"10"
> :y shoeSize int"10"
> 
> Now we got it! int"10" is not a string now; it's what we want it to
> mean: an integer. Damn. The entailment
> 
> :x age :z
> :y shoeSize :z
> 
> still holds...
> 
> Is there something wrong with the above modeling practice? Should
> int"10" itself be considered untidy, like those untyped literals?
> Are all those folks who chose the above modeling style dumb? NO, they
> are not. Above, the properties age and shoeSize are merely used to
> restrict the valid interpretations of :x and :y. There is no claim that
> shoeSize is a property that holds between shoes and "shoe sizes". It's a
> property that holds between shoes and integers, thereby restricting the
> intepretation of :y. Just as well, shoeSize could be defined as a
> property that holds between shoes and strings/reals/etc.
> 
> An overwhelming majority of applications use exactly this metaphor. For
> example, look at the AdobeXMP documentation, where the range of
> xapDynA:Volume is defined to be a Real. Did those folks want to assert
> that the abstract concept of volume coincides with real numbers? No. Or,
> what about CC/PP's
> 
> :x displayWidth int"640"  ?
> 
> After all, display width is not measured in integers, but in inches or
> centimeters...
> 
> My conclusion is that it is not necessary to claim that "John Smith"
> represents a person (and call for untidy literals), in order to achieve
> correct modeling. And, by no means have applications and APIs to be
> changed to reflect this "insight". The applications, and their
> developers, possess a consistent conceptual model of what dc:Creator or
> age or shoeSize mean. These apps run just fine. For the lack of
> conceptual necessity of "thinking untidy" I'm suggesting: don't touch
> running systems.
> 
> Sergey
> 
> 
> 
> 
> 
> 
> 
> 
Received on Thursday, 26 September 2002 04:35:03 EDT

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