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Re: Semantic Web and First Order Logic

• To: xml-dev@l...
• Subject: Re: Semantic Web and First Order Logic
• From: Miles Sabin <miles@m...>
• Date: Fri, 21 Mar 2003 02:30:33 +0000
• In-reply-to: <004c01c2ef48$09e43630$6401a8c0@tbp1>
• References: <15725CF6AFE2F34DB8A5B4770B7334EEEAD0AB@h...> <004c01c2ef48$09e43630$6401a8c0@tbp1>
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Thomas B. Passin wrote,
> I do not think that ordinary business applications today come close
> to using full FOL.  Mostly things run on ordinary assertions (this
> would cover relational databases), and sometimes on rulesets. 
> Ordinary markup languages are EC - Existential Conjunctive - only one
> sector of FOL - and they are almost always enough for these kinds of
> uses.

I disagree.

Actually, I'll go further. Even full first-order logic is too 
restrictive to express many trivial inferences straightforwardly. For 
example,

  There's a 5% surcharge on primary coloured widgets
  x is a red widget
  red is a primary colour

therefore,

  There's a 5% surcharge on x

This is easy to express in second-order logic, or in first-order logic 
plus set theory (the "plus set theory" bit means that you can forget 
about decidability). Not so easy in plain first-order logic.

Expressive power, decidablity ... pick one.

Cheers,


Miles

• Follow-Ups:
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    • From: "Thomas B. Passin" <tpassin@c...>

• References:
  • Semantic Web and First Order Logic
    • From: "Bullard, Claude L (Len)" <clbullar@i...>
  • Re: Semantic Web and First Order Logic
    • From: "Thomas B. Passin" <tpassin@c...>

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