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

From: Sandro Hawke <sandro@w3.org>
Date: Thu, 10 Oct 2013 09:11:50 -0400
To: Pat Hayes <phayes@ihmc.us>,David Booth <david@dbooth.org>
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>
Message-ID: <3a9b6c0c-c8a2-47da-9462-cca86566842e@email.android.com>

Pat Hayes <phayes@ihmc.us> wrote:
>Hi David
>This is NOT an official WG response, but only an informal note to
>explain some of the background thinking and discussions behind some of
>the decisions we took. Please don't copy this to the public comments
>list. I added Sandro to the CC list as he seems interested in this
>The 2004 semantics document tried to do (at least) two things at once.
>It is a formal, normative description of the semantics, but it also
>tried to be a "tutorial" in various places, including in the section
>you refer to and the extended glossary. This introductory material has
>gotten some good reviews (thanks) but also has gotten some criticism,
>especially with regard to its appropriateness for inclusion in a
>normative standard document. And for sure, it made the document a lot
>longer than it would have been without it, and the sheer length of the
>RDF specs has come in for a lot of criticism. And for some readers, it
>is an irritating distraction. 
>Early in this WG, after some extended discussions, we decided that the
>public interest would be better served by separating the
>explanatory/tutorial/introductory material from the formal technical
>normative material, and moving the former to a different document, a
>kind of introduction/tutorial/primer document that is yet to be
>written, and thereby making the normative technical document shorter
>and crisper. This sacrifices readability for precision and exactness,
>but there was a consensus in the WG that at this time in the evolution
>of RDF, precision and exactness (and comparative brevity) were more
>important than introductory exposition, in the actual normative
>specification.  This is why the material that you now miss, is missing.
>(You may also notice that the RDF1.1 Concepts document is also much
>shorter and brisker than the 2004 version, for the same reasons.) As I
>say, the plan was (and still is) to move this all to a 'primer'
>document rather than abandon it entirely, but this is why its not in
>the actual semantics document. 
>The short "intuitive summary" section on which you commented earlier
>represented an editorial lapse on my part when drafting the new
>document, where my old teaching instincts overwhelmed my responsibility
>as WG editor. Your comment made me realize the error of my ways. 


   - Sandro

>On Oct 9, 2013, at 10:16 PM, David Booth wrote:
>> 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:
>In the above sentence, I was using the word "refer" in its normal
>English usage, informally. But in any case, the point still stands:
>they might be referring to things in the universe of a different
>> 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
>I don't accept that it does make this clear. 
>> , 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.
>The notions of reference (what a name refers to, or denotes) and truth
>are pre-theoretic. They are part of our ordinary understanding of the
>world. Interpretations simply formalize (if one can call such a simple
>construct a 'formalization") this intuition so that one can do some
>mathematics with it. The idea of this section was to use the ordinary
>English words "refer" and "interpret" to re-state the truth conditions,
>just to show how mind-numbingly obvious they are, and hopefully to
>indicate how the formal machinery corresponds closely to the
>pre-theoretic ideas. However, this purpose is undermined if this
>section is understood formally rather than intuitively. 
>But, as I say, I now think that this idea, of trying to connect the
>formal notions to an intuition, was probably a mistake in this document
>and went against the spirit of a WG decision. 
><<Other in-line responses, below, are part of our continuing, um,
>debate, and are aside from discussions of the RDF documents.>>
>> > 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.
>That is exactly what it should *not* be, in order to convey the point
>it was intended to be conveying. 
>>  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*
>No, that is not the right way to understand it. Truth and
>satisfiability are not the same thing at all. (That pigs can fly, is
>satisfiable.) To say that a graph (or any other assertion or sentence)
>is true, is to say that when it is interpreted *in the actual world*,
>its truth-value is true. That is the pre-theoretic, intuitive, notion.
>Someone says something, you figure out *what* they are saying, and you
>judge whether it - what they are saying - is true. Nothing in that
>account mentions interpretations. It does mention, implicitly, the
>truth conditions (section 5) and we could say that it *presumes* an
>interpretation that the speaker and hearer have in common. And that is
>where the naivitée of this naive account is displayed, of course, that
>implicit assumption of a common interpretation; because when we have
>the kind of distancing between publisher and reader that is inevitable
>on the semantic web, and communicate using IRIs which have no assumed
>common background of linguistic meaning, we cannot presume this common
>shared interpretation, this "common ground"
>or http://plato.stanford.edu/entries/discourse-representation-theory/.)
>So this is where the interpretation idea comes in, because we have to,
>as it were, survey the possible things you might mean when you publish
>some RDF. We don't know what world you are talking in, so we have to
>consider all *possible* worlds. Which is what interpretations are (the
>thin, pale shadows of formalizations of).
>Long - very long - story short, the analysis of real linguistic
>communication - including Web communication - between cognitive agents
>(people, mostly) involves model-theoretic ideas, but it also involves a
>*lot* more. RDF, indeed the entire semantic web, is a tiny part of this
>larger picture, and can be fitted into it in one small corner. But in
>order to be useful, it does need to be fitted into it accurately. 
>> : 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**
>The one that is presumed when we talk (pre-theoretically) about what
>people are referring to when they say "Everest" (for example), and when
>we make judgements of the truth or otherwise of their utterances in the
>actual, real, world we are all talking about. Yes, exactly. 
>> .  But that would be a very bad way to write
>Try telling that to linguists. Or to literary theorists, or historians,
>or philosophers of language, or indeed pretty much anyone who uses
>language professionally. Not only is this not a bad way to write, its
>the ONLY way to write if we are trying to anchor model theory in an
>intuitive description of how communication actually happens. Except,
>calling the actual world "unspecified" seems a little strange. 
>> , 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.  
>It is implicit, yes, but I don't know what kind of assumptions you are
>appealing to by calling this a big no-no. Contexts are usually
>implicit, right?
>> 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
>> ]]
>> (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.  :)
>Well, you weren't meant to read that, obviously. But my dear fellow,
>*have* you read the books, in fact? Is it really condescending for me
>to suggest that you might want to read up something a little more
>extensive than a few paragraphs that I wrote about RDF, before claiming
>that you have discovered a new way to understand model theory, or
>setting out to correct my misunderstanding of it, or telling me that my
>perspective is too limited? I don't mean to pull rank on you here, but
>I have been studying this stuff now, as well as teaching it, for about
>40 years. For a few years, I invented new model theories for a living.
>God knows there are a lot of things I don't fully understand, but
>model-theoretic semantics is one topic I really do have pretty
>thoroughly grokked. 
>> 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
>> 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
>> recommendations, which have been tracked as ISSUE-149.
>> Section 5.2 is an informative section and was only put in as an
>> easier-to-understand gloss of some of the the preceeding more-formal
>> section.  Both your comment and the ensuing discussion have made it
>> 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
>> your concern?  If you are satisfied, then the section will be removed
>> 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
>>> 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
>>> is true exactly when: . . . " to: "An RDF graph is true exactly when
>>> 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
>>> 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
>>> Also point 4 mentions "these interpretations", but it isn't clear
>>> 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
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Received on Thursday, 10 October 2013 13:11:53 UTC

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