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Re: [FLD] review of Appendix Hebrand Structures

From: Michael Kifer <kifer@cs.stonybrook.edu>
Date: Thu, 6 May 2010 01:57:21 -0400
To: Jos de Bruijn <jos.debruijn@gmail.com>
CC: RIF <public-rif-wg@w3.org>
Message-ID: <20100506015721.3081dadf@kiferserv>
Jos, thanks for the comments. I have addressed all the issues you mentioned
except for the following: 

> 1- The standard reference for the answer set semantics is [1], in which
> Gelfond and Lifschitz define the answer set semantics for disjunctive logic
> programs with classical negation.


> 2- In the definition of Herbrand domain, it seems to me that the second and
> third bullet are redundant, since they are implied by the first

Why? These terms (mentioned in those bullets) are equal according to our
semantics. How does it follow that they are equal in Herbrand structures if
those bullets are not included?

> 3- In the definition of Herbrand Semantic Structure, in the symbol HD_sg
> (the subdomain for signature sg), 'sg' should use the sans serif font, as it
> does in other places in the sentence.


> 4- Definition Consistent Semantic Structure: "cannot both be" -> "are not
> both" (twice)


> 5- Definition Ground Instantiations: it is not clear whether the definition
> applies also to subformulas, so I suggest the following replacement:
> "non-group, non-document formula" -> "non-group formula that is a subformula
> of a group formula"

OK. But we have to say "non-group formula that is a direct subformula ..."
We never defined what a direct subformula is, but I suppose it is clear.

> 6- Paragraph before the definition "Empty Herbrand Structure": the first
> sentence seems to suggest that there is a notion of "undefined" in the
> standard stable model semantics. This is not the case.

OK. I meant 3-valued stable models. But I deleted
the mention of stable models in that
sentence, since empty models are not really used to define even 3-valued
stable models.

> I would like to see at least comments 1, 5, and 6 addressed before the
> document is published.

OK, so everything seems to be addressed except #2.


> Cheers, Jos
> [1] Michael Gelfond, Vladimir
> Lifschitz<http://www.informatik.uni-trier.de/%7Eley/db/indices/a-tree/l/Lifschitz:Vladimir.html>:
> Classical Negation in Logic Programs and Disjunctive Databases. New
> Generation Comput.
> 9<http://www.informatik.uni-trier.de/%7Eley/db/journals/ngc/ngc9.html#GelfondL91>(3/4):
> 365-386 (1991)
Received on Thursday, 6 May 2010 05:57:55 UTC

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