Pat and Doug, (01)
PH
>> But there are no "contexts" in RDF or OWL or Common Logic, for that
>> matter. So I repeat, I have no idea what he means. (02)
DF
> Common Logic does not ban contexts. In RDF, one could consider the graph
> in which a statement appears to be its context. (03)
Common Logic lets quantified variables refer to anything of any type.
In principle, that would allow variables to refer to propositions,
situations, or anything else that you might consider a context. (04)
However, a usable theory of contexts requires some metalevel mechanism
to state that a certain block of text (in Common Logic or whatever
logic you prefer) expresses a certain proposition. (05)
The IKRIS project produced the IKL language that adds one additional
feature beyond CL: the keyword 'that', which provides the mechanism.
For example, (06)
English: Tom believes that two plus two equals 4. (07)
IKL: (believes Tom (that (= 4 (+ 2 2)))) (08)
Technically, 'that' provides the function of back quote in LISP or KIF,
which enables references to a block of text that contains variable bound
to quantifiers outside that block. If you have a theory of context, you
could use a block of text marked by 'that' to represent your contexts. (09)
Several Cyclers participated in the IKRIS project, and they agreed that
IKL is sufficient to express statements written in CycL. (010)
For a selection of the IKRIS reports, see http://www.jfsowa.com/ikl (011)
John (012)
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