Pat, Chris, and Wacek, (01)
I had overlooked that axiom because in CGs, there is no
explicit operator for 'and'. A CGIF statement is just a
set of concept and relation nodes with no markers between
nodes (even blanks are optional). The conjunction of two
statements is just a bigger set of nodes. (02)
PH> McCarthy claims that and-distribution applies to both:
>
> (ist c (p & q)) iff ( (ist c p) & (ist c q) ) (03)
I would accept it also, and I agree with Chris and Wacek
that the suggested counterexample that involves time and
a collection of events is unconvincing. (04)
It is similar to the following example that has been cited
since antiquity: (05)
A true sentence when stated in the past tense: (06)
"Liz Taylor had seven husbands." (07)
A sentence that was never true in the present tense: (08)
"Liz Taylor has seven husbands." (09)
Re use of the word 'context' in knowledge representation: (010)
If you want to go back to the Ur-etymology, the word refers to
something that is woven together (as in textiles). But even in
classical Latin, it had a metaphorical extension to a weaving
of words. The two basic meanings from a typical dictionary
(Merriam-Webster) are (011)
1. The parts of a discourse that surround a word or passage and
can throw light on its meaning. (012)
2. Milieu or environment. (013)
The first sense is the more basic, and I interpret the second
as a derivative sense that takes in more of the surroundings
than just the words. (014)
My recommendation is the following: (015)
1. If you don't like the word 'context', then don't use it. (016)
2. But if you do think the word is sufficiently useful to be
applied to formal knowledge representations, then state
a clear, precise definition that is within the range of
meaning in a conventional dictionary (such as M-W or
any other well-edited dictionary you prefer). (017)
3. My own preference is to focus on the phrase "parts of the
discourse" and to state a formal definition in terms of
some mechanism for selecting a chunk of text. (018)
4. That is what I did for conceptual graphs. I defined a
context delimiter (represented by a box) as a container
for some text (a set of graphs) that states whatever is
is true in a context (as in McCarthy's ist predicate). (019)
5. In a mapping to and from IKL, I would map the contents of
the CG context box to an IKL sentence s in "(that s)". (020)
I don't really care whether IKL uses the word 'context',
since I am using it only for a syntactic mechanism in CGs.
But as I said, the semantics of the contents of the CG box
can be defined by axioms stated outside the box (or outside
the IKL that-expression in a translation of the CG contents). (021)
John (022)
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