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RE: Desirata for Symbols (was Re: What do the ontologists want)

From: Danny Ayers <danny@panlanka.net>
Date: Sun, 20 May 2001 22:35:44 +0600
To: <www-rdf-logic@w3.org>
Message-ID: <EBEPLGMHCDOJJJPCFHEFCEKJDHAA.danny@panlanka.net>
RE: Desirata for Symbols (was Re: What do the ontologists want)us:elvis
job(rock'n'roll)

wales:elvis
job(saint)

Though some might same these are equivalent.


---
Danny Ayers
http://www.isacat.net

  -----Original Message-----
  From: www-rdf-logic-request@w3.org [mailto:www-rdf-logic-request@w3.org]On
Behalf Of Ziv Hellman
  Sent: 20 May 2001 20:33
  To: Sandro Hawke; pat hayes
  Cc: www-rdf-logic@w3.org
  Subject: RE: Desirata for Symbols (was Re: What do the ontologists want)




  >
  > pat:
  > > sandro:
  > > >What possible advantage does "urn:elvis" (or any other
  > URI-like thing)
  > > >have over "elvis" as a logic symbol?
  > > >
  > > >1.  We can prevent unintentional re-use.   This is like
  > > >    com.sun.SomeJavaClass or w3c_some_C_library_function.
  > Doing this
  > > >    allows us to skip a symbol translation stage in reasoning about
  > > >    two different expressions.
  > >
  > > Several problems with this include the fact that often, with names,
  > > one NEEDS to have 're-use' in order to refer to something. That is
  > > largely what names are for in social use of language, if you think
  > > about it. But I have argued this to death in earlier threads.
  >
  > Er yes -- that's why I said "prevent UNINTENTIONAL re-use."
  >
  > In logic terms, I believe this feature lets you make skolum
  > functions/constants.
  >

  Skolem functions are simply tools for eliminating existential quantifiers.
For example, if one states that in a given population every person has a
brother

  (ForAll x) (ThereExists y) Brother(x, y)

  then defining a Skolem function f provides a way of expressing a
particular brother in each case -- given x, since you known that x has a
brother, you can use f(x) to refer to "x's brother"

  (ForAll x)  [ (ThereExists y) Brother(x, y) --> Brother( x, f(x) ]

  Which is all well and good ... but still has no bearing for the question
of 'what possible advantage does "urn:elvis" (or any other URI-like thing)

  have over "elvis" as a logic symbol?'




  Cheers,

  Ziv
Received on Sunday, 20 May 2001 12:40:22 UTC

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