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Fwd: Re: RDF Semantics - Intuitive summary needs to be scoped to interpretations (ISSUE-149)

From: David Booth <david@dbooth.org>
Date: Wed, 09 Oct 2013 23:16:39 -0400
Message-ID: <52561C17.3030302@dbooth.org>
To: Pat Hayes <phayes@ihmc.us>
CC: Antoine Zimmermann <antoine.zimmermann@emse.fr>, www-archive <www-archive@w3.org>, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>, Ivan Herman <ivan@w3.org>
Hi Pat (and others),

I would not raise an objection to deleting the Intuitive Summary, but I 
think there would be a loss to the public in deleting it.  I also really 
liked the explanation of interpretations that you included in the 2004 
version, and miss it in the current draft.  It really gave very good 
insight into the concept.  So personally, I think a better solution 
would be to add back your explanation of interpretations and tweak the 
Intuitive Summary section as needed.

You mentioned this concern:
[[
Consider:

"An RDF graph is true under a given interpretation exactly when:
 >
 > >
 > > 1. the IRIs and literals in subject or object position in the
 > > graph all refer to things,

But suppose that they refer to things that are not in the universe of 
the given interpretation, then this is false.
]]

But AFAICT that is impossible, because "refer" is defined in sec. 4 to 
be relative to an interpretation:
http://www.w3.org/TR/2013/WD-rdf11-mt-20130723/#notation
[[
The words denotes and refers to are used interchangeably as synonyms for 
the relationship between an IRI or literal and what it refers to
**in a given interpretation** . . . .
]]
(my emphasis).   And the wording that I suggested makes clear what 
interpretation is intended, so the IRIs and literals *cannot* refer to 
things outside of that interpretation's universe.

Also, I don't know what you mean when you wrote:
[[
No doubt David would respond, but readers should be *obliged* to think 
about interpretations, and then my reply would be, OK, but if so then 
this section is inappropriate in the first place, so let us delete this 
section.
]]

Why would that section be inappropriate if readers are obliged to think 
about interpretations?  It seems to me to give a fairly concise summary 
of the formal approach taken.

Finally, at the risk of restating the potentially obvious, I do not see 
how anyone could possibly understand the formal semantics without 
understanding the idea of interpretations, since they are so central to 
the semantics.

 > On Oct 4, 2013, at 10:51 AM, Peter Patel-Schneider wrote:
 >
 > > In my opinion the divergence boils down to Pat believing that this 
informative section should be more informal and David believing that it 
has to be more formal.

I don't exactly think it has to be more formal, but just that: (a) it 
needs to mention interpretations, because that concept is so central to 
the formal semantics; and (b) the statement about the conditions under 
which a graph is true *needs* to be scoped to an interpretation to make 
any sense at all.  If one talks about a graph being true, without 
mentioning an interpretation, IMO the most sensible way to understand 
such a statement is to take it as meaning that the graph is 
*satisfiable*: that there *exists* an interpretation under which the 
graph is true, and hence we can take the graph as being true. 
(Conversely, if the graph is not satisfiable then we cannot take it as 
being true.)  OTOH, such a statement could be taken to mean that the 
graph is true **in some unspecified interpretation**.  But that would be 
a very bad way to write, because the interpretation under which the 
graph is true would be an implicit unbound variable, which as we all 
know is a big no-no.  Instead, the problem can be easily solved by 
adding "under a given interpretation" to the sentence.  (Of course, the 
notion of an interpretation should first be explained.  But that is a 
different omission that should be addressed anyway.)

And regarding this:
http://lists.w3.org/Archives/Public/public-rdf-wg/2013Oct/0079.html
[[
I know, from extensive off-line email discussions with David, that he 
does not properly understand the intuitive foundations of semantics in 
any case, so I am not inclined to accept his rather condescending advice.
]]
(Wow, you're calling *me* condescending, after repeatedly telling me to 
"go read a book"???)  That's both: (a) quite a projection; and (b) 
*really* unfair and unhelpful.  Fortunately I'm thick skinned and I have 
a good sense of humor.  :)

Thanks,
David

-------- Original Message --------
Subject: Re: RDF Semantics - Intuitive summary needs to be scoped to 
interpretations (ISSUE-149)
Date: Wed, 09 Oct 2013 15:06:19 -0700
From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
To: David Booth <david@dbooth.org>
CC: public-rdf-comments <public-rdf-comments@w3.org>

Greetings David:

This is an official RDF working group response to your message
http://lists.w3.org/Archives/Public/public-rdf-comments/2013Oct/0010.html
on Section 5.2, Intuitive Summary, of the RDF 1.1 Semantics document.
The Working Group thanks you for your concerns on this aspect of the RDF
recommendations, which have been tracked as ISSUE-149.

Section 5.2 is an informative section and was only put in as an short,
easier-to-understand gloss of some of the the preceeding more-formal
section.  Both your comment and the ensuing discussion have made it clear
that the section is not achieving its purpose.  As there appears to be no
consensus on what changes, if any, should be made to the section, it is the
intent of the working group to just remove the entire section.

Could you please respond to public-rdf-comments@w3.org as to whether
removing this non-normative, non-formal section would satisfactorily address
your concern?  If you are satisfied, then the section will be removed from
the document.

Peter F. Patel-Schneider
for the W3C RDF WG


On 10/01/2013 10:15 PM, David Booth wrote:
> https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-mt/index.html
>
> Section 5.2 Intuitive summary needs to be scoped to a particular
> interpretation or set of interpretations.  At present the interpretations
> are implicit, and this is misleading because it suggests that the notion of
> a graph being true is somehow independent of an interpretation, whereas in
> fact the truth of a graph critically depends on the interpretations that are
> chosen.
>
> I suggest rewording the first sentence of this section from: "An RDF graph
> is true exactly when: . . . " to: "An RDF graph is true exactly when there
> exists an interpretation such
> that: . . . "
>
> Also, the verb "interpret" is being used in this clause: "2. there is some
> way to interpret all the blank nodes in the graph as referring to things,",
> but that causes confusion with the notion of an interpretation (which is a
> function).  It would be better to use a different verb at this point.
>
> Also point 4 mentions "these interpretations", but it isn't clear what
> interpretations are meant.  Perhaps it means the results of the verb
> "interpret" in item 2?  In which case, a different word should be used here
> also.
>
> Thanks,
> David
>
>
Received on Thursday, 10 October 2013 03:17:07 UTC

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