Re: SUO: What people mean
"West, Matthew MR SSI-GREA-UK" <Matthew.R.West@is.shell.com>:
>In a recent message you said (and I paraphrase):
>
>In logic when you say (married Matthew Lydia) it means married for all time.
>
>The bad news is that although this may be formally correct, when people
>write this (as they do) what they usually mean is (married Matthew Lydia)
>NOW (or at least at time of writing). This is what I call the snapshot
>approach to change management (really the "do nothing" scenario).
Yes, I know. But if someone writes *any* axiom in almost any formal
logic and then claims that it is supposed to be true NOW, but not
true somewhen else, then they are just mis-using the formalism.
(Modal logicians read to end before exploding.) Logics don't mention
a 'time of writing'. Logics are NOT like natural languages!
They might want to say they are writing their ontology in NL. OK,
good luck to them, but then they are playing a different game: that
isnt what many of us mean by 'ontology'.
Pat
PS. Modal logics can distinguish 'true (implicitly NOW)' from 'will
be true (at some time in the future of NOW)' and 'was true(at some
time in the past of NOW)'. So indeed logics can have tenses, like NL.
But notice it is the same NOW in all three cases. The modal axioms
can be thought of as being about time relationships, but they provide
no way for the logical sentences themselves to be 'situated' in time:
there is no way for NOW to actually change in these logics, so they
arent anything like NL in this respect.
Some more recent formalisms like linear and hybrid logics do claim to
cover some of the indexicality of NL. I havn't seen anyone seriously
urging their use in ontologies, though.
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