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Re: Another try.

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 28 Feb 2012 22:16:29 -0600
Cc: RDF-WG Group <public-rdf-wg@w3.org>
Message-Id: <86C22432-0AE2-4151-85C2-73223ACB7817@ihmc.us>
To: Dan Brickley <danbri@danbri.org>

On Feb 28, 2012, at 10:37 AM, Dan Brickley wrote:

> On 28 February 2012 16:54, Pat Hayes <phayes@ihmc.us> wrote:
> 
>> First, it was abundantly clear from the very beginning of the RDF WG activity that RDF/S (and DAML/OIL and subsequently OWL) were understood to be timeless logical languages.
> 
> Put it this way...
> 
> The first public RDF Working Draft, http://www.w3.org/TR/WD-rdf-syntax-971002/
> 
> <?namespace href="http://docs.r.us.com/bibliography-info" as="bib"?>
> <?namespace href="http://www.w3.org/schemas/rdf-schema" as="RDF"?>
> <RDF:serialization>
>  <RDF:assertions href="http://www.bar.com/some.doc">
>    <bib:author>
>      <RDF:resource>
>        <bib:name>John Smith</bib:name>
>        <bib:email>john@smith.com</bib:email>
>        <bib:phone>+1 (555) 123-4567</bib:phone>
>      </RDF:resource>
>    </bib:author>
>  </RDF:assertions>
> </RDF:serialization>
> 
> While the document's author may be eternally the same, John's name,
> email and phone are likely more volatile. While the schema's author
> could've baked temporally-qualifying observations into the prose of
> the property definition (e.g. 'current or former...'), in practice few
> do this.

Hmm. OK, but why is this, I wonder? Several possible answers. 1. Users might feel that many properties, while liable to change, in fact are stable enough that its worth treating them as timeless. (People's names dont change very often, and the cases that do arise (marriage, usually) are of a wellknown and kind of predictable sort.)  2. Users assume that the information is being recorded at a known time and will be timestamped somehow, and the necessary updating will be done semiautomatically (eg figuring out your current age from the recorded age and the date it was recorded.) 3. LIke 2, but users just dont care about the information getting old and decaying, because nothing important is going to be inferred from it. (FOAF age as opposed to age recorded by the SSA.) 4. Users just dont think about the issue at all, and arent even thinking about time-relative information versus stable timeless information.

Any insight into which of these (or any others) is closest to the truth? 

BTW, I can attest that what one might call 'hard' users of ontological data, eg in bioinformatics and health sciences, are very much concerned about this issue and are getting tied in knots over it. 

> 
> <?namespace href="http://www.nist.gov/RDFschema" as="NIST"?>
> <?namespace href="http://www.w3.org/schemas/rdf-schema" as="RDF"?>
> <RDF:serialization>
>  <RDF:assertions href="John_Smith">
>    <NIST:weight>
>      <RDF:resource id="weight_001">
>        <NIST:units href="#pounds"/>
>        <RDF:PropValue>200</RDF:PropValue>
>      </RDF:resource>
>    </NIST:weight>
>  </RDF:assertions>
> </RDF:serialization>
> 
> ... not to mention his weight.  (And I wish I weighed now what I
> weighed in 1997.)
> 
> Anyway, this pretty much set the tone for everything that followed, in
> terms of RDF-in-practice.
> 
> I know perfectly well you could've made us a lovely temporal logic or
> whatever instead; but the RDF Core job wasn't to do that, but to come
> up with a more formal story that covered as much as possible of
> RDF-in-practice. Which it did, except for the aspect that people
> stubbornly keep defining and using properties for stuff that changes,
> even if the smallprint says not to. We went as far as we could without
> creating another place to stuff information. It seems now we're
> considering doing just that.

Put another way, our technology has already created such a place for us, and we are considering making it official. 

Pat


> 
>> So if Dan or anyone else is thinking that RDF is going to eventually become a time-embedded language in which assertions have a temporal state, then forget it.
> 
> I don't believe I suggested that, and I like the direction of your
> recent proposals.
> 
> cheeers,
> 
> Dan
> 
> 

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Received on Wednesday, 29 February 2012 04:17:00 UTC

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