[FLD] review of Appendix Hebrand Structures

I reviewed the current version of the FLD section 8 Appendix: A Subframework
for Herbrand Semantic Structures
I found no major issues. Find my comments and suggestions below:

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
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"
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.

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


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)

-- 
Jos de Bruijn
 Web:          http://www.debruijn.net/
 LinkedIn:     http://at.linkedin.com/in/josdebruijn