Am Mittwoch, 26. Februar 2020 15:51:21 UTC schrieb linas:
>
> Hi Alex,
>
> You might need ...@Nil Geisweiller <javascript:> to give you the full,
> complete reply, as I'm just not that good with the URE. But I think I can
> help clarify a few issues.
>
> I didn't test, but I think that maybe your bug goes away if you make the
> target into this:
>
> (And (Present (Variable "person1")) (Present (Variable "person2"))
> (Not (Indentical (Variable "person1") (Variable "person2"))))
>
> which basically says: "the variable 'person1' must be grounded by
> something that is present in the current atomspace at this moment in time.
> ... and also person2, and the groundings are not by the same atom" .
>
Nice, thank you! Yes adding the PresentLinks to the target reduced the
number of results that came with the fuzzy-conjuction rule to one and the
one is the right one, alice and bob. Unfortunately, the IdenticalLink still
doesn't get a non-default truth value automatically and if I pre-define it
as described in the problem statement above, the NotLink also still doesn't
play game and stays at default. Hopefully @Nil Geisweiller (or anyone else)
has an idea on how to solve that one.
(SetLink
(AndLink
(InheritanceLink (stv 1.000000 1.000000)
(ConceptNode "bob") ; [510da4194021b685][1]
(ConceptNode "human") ; [61b8bd8c84744a4d][1]
) ; [84ecb7fcf35adfdf][1]
(PresentLink
(ConceptNode "bob") ; [510da4194021b685][1]
) ; [c8aee4e806a8b606][1]
(InheritanceLink (stv 1.000000 1.000000)
(ConceptNode "alice") ; [6edb97fb269f42cf][1]
(ConceptNode "human") ; [61b8bd8c84744a4d][1]
) ; [f38e20568bbc0db3][1]
(NotLink
(IdenticalLink
(ConceptNode "bob") ; [510da4194021b685][1]
(ConceptNode "alice") ; [6edb97fb269f42cf][1]
) ; [9f4a3813ae99a91d][1]
) ; [f4f3e04ea1b33133][1]
(PresentLink
(ConceptNode "alice") ; [6edb97fb269f42cf][1]
) ; [fad3b63524d57e2d][1]
) ; [84c85ed40fe08dfd][1]
) ; [de5b9063ff45cdff][1]
> I call this a bug because the pattern matcher should have implicitly
> assumed this, without you having to explicitly say "present". I'll see if I
> can fix this bug "real soon now".
>
I agree, why would someone be querying for things not present (accept with
a combination of (NotLink (PresentLink someTarget)) ). Thanks for putting
that on your todo list :)
>
> The other one, the throw on (cog-evaluate! target), that's an interesting
> one. So, if you read the error message very carefully, it is saying that
> it does not know how to evaluate (Inheritance (Variable "person1")
> (ConceptNode "human")) ... which makes sense, because how would you
> evaluate that, anyway? I find it interesting because we could "fix" this
> in an interesting manner: if cog-evaluate! gets something that has (free)
> variables in it, it should implicitly assume a SatsifactionLink. For your
> example, this works: (cog-evaluate! (Satisfaction target)) -- that is,
> there does exist in the atomspace at least one grounding for the variables
> such that all clauses are satisfied.
>
What I found especially interesting (or rather confusing now that I know
more) is that it had no problem with the target not including the
InheritanceLinks and then complained about those instead of the ungrounded
variables. I'm not sure that assuming an implicit SatisfactionLink is
cleaner than giving a helpful ("We can't handle this, because of ungrounded
variables. Have you considered wrapping in a SatisfactionLink or other
binding mechanism?") error message. The later part would be more cumbersome
for people I guess, but they might learn something on the way...and it
avoids people thinking it'll assume this while it's assuming
that...Whatever solution, whatever is happening should be as transparent as
possible I think.
Best,
Alex
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