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Re: Comments on ioctl (was: Re: big issue (2001-09-28#13))

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 8 Oct 2001 16:53:17 -0500
Message-Id: <p05101012b7e7cf44b2c8@[]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
>At 11:51 AM 10/5/01 -0500, Pat Hayes wrote:
>>However, what I think IS characteristic of all kinds of literal is, 
>>that they bear a very close kind of relationship to their 
>>denotations, in that one can *compute* the denotation from the 
>>literal. It wears its meaning on its sleeve, as it were. You don't 
>>need to go off looking for assertions *about* its meaning; you can 
>>tell just by looking at the literal itself what its denotation is 
>>(maybe using some literal-defining conventions , e.g. knowing that 
>>it is a decimal numeral written from left to right, but those are 
>>fixed outside the assertional language and are considered part of 
>>the lexical definition of the vocabulary.) Obviously,  being its 
>>own denotation is a particularly simple case of that, but its not 
>>the only possible case. So Id suggest altering this to:
>>a literal is a name whose denotation can be computed from the name alone
>Yes!  I think this captures something I've been struggling to 
>articulate.  (I read this after my recent post to RDF-logic.)

Havnt had time to look at RDF-logic yet today :-)

BTW, Peter P-S seems to disagree with this characterization of 
literals, I'm trying to get on his wavelength right now.

>>Can a literal label an arc? Well, that is up to the Arc Police, ie 
>>us; but, *could* a literal label an arc? Yes, as far as the model 
>>theory is concerned, though that would have some fall-out in the 
>>treatment of literals in RDFS. Right now the MT tries hard to keep 
>>literals at a safe distance, as it were, since their status is 
>>cloudy, and to maintain that hands-off style while also allowing 
>>literals as subjects or arc labels would be tricky. But if we were 
>>to take some kind of Big Decision to allow literals to be more 
>>closely integrated with the things URIs denote, then the MT would 
>>actually get easier. Easiest of all from the MTs point of view 
>>would be to just toss URIs and literals all together and give them 
>>a uniform semantics
>Hmmm... according to the MT as it stands, the thing denoted by an 
>arc label must have an extension which is the set of pairs that can 
>appear at each end of the arc.  Is it reasonable that this set can 
>be computed from the literal used to label the arc?

In a sense, yes; eg, given the denotations of the nodes at the ends, 
you can compute the truthvalue of the relation (ie whether or not 
that pair in in the extension).  So the relational extension only 
needs to be RE rather than recursive. In your example:

>I suppose so:  I can imagine an arc label "<", for which one can 
>compute a relational extension:
>    { <"0","1"> <"0","2"> <"0","3"> ...
>      <"1","2"> <"1","3"> ...
>      etc.  }

you can't compute the entire infinite set, but given any pair, you 
can quickly figure out if its in the set or not.

>(Practical rules of computation would need to take into account 
>other details like signs, leading zeros, nu8mber base, other lexical 
>variations of number representation.  I suppose that arc-label 
>literal should be "decimal<" or suchlike.)

Right. Leading zeros and suchlike stuff is one reason why you have to 
say 'compute from' rather than 'is'.


PS. Graham, on another topic altogether, I think Ive managed to shut 
up that noisy fellow Ray on rdf-comment.

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Received on Monday, 8 October 2001 17:53:23 UTC

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