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Re: Comments on Last-Call Working Draft of RDF 1.1 Semantics

From: Michael Schneider <schneid@fzi.de>
Date: Sun, 27 Oct 2013 21:41:41 +0100
Message-ID: <526D7A85.4060404@fzi.de>
To: Pat Hayes <phayes@ihmc.us>, "public-rdf-comments@w3.org Comments" <public-rdf-comments@w3.org>
CC: Guus Schreiber <guus.schreiber@vu.nl>
Hello Pat,

in this mail, I will respond exclusively to your answers regarding 
ISSUE-166,
that is, those that are not related to my comment on datatype maps 
(ISSUE-165).

In summary, I am happy with all your responses regarding issue 166.
See below for details.

On 23.10.2013 18:10, Pat Hayes wrote:

> Regarding ISSUE-166, we have made several changes in response to
> some of your points, as listed below.
>
>> NON-URGENT ISSUES (NOT DESIGN-RELATED):
>>
>> * 3: The chapter introduces the term "entailment regime",
>>   but does not say much about it. As this term is also
>>   introduced and quite intensively used in the SPARQL 1.1 spec
>>   (in particular by the SPARQL Entailment Regimes spec), I
>>   suggest to be a little more elaborate on the term, in order
>>   to avoid that the terms are not understood differently in
>>   the contexts of the two specifications.
>
> Good point. I have made this edit, with a reference added:
>
> Each semantic extension defines an entailment regime (used here
> in the same sense as in the SPARQL 1.1 Entailment Regime
> recommendation [SPARQLENTAIL]) of entailments which are valid
> under that extension.

Ok.

>> * 4, 2nd par: I would change the order of "referent and
>>   denotion" to "denotion and reference" to match the order
>>   of the two corresponding terms mentioned earlier in the text:
>>   "denotes and refers to".
>
> Agreed, done.

Thanks.

>> * 5.3 (and for other entailment regimes as well): I suggest
>>   to always be explicit on the entailment regimes, when it
>>   comes to the terms "satisfies", "entails", etc. So it should
>>   always be "simply entails", or "RDF entails", instead of only
>>   "entails", even if this may be obvious from the context (it
>>   probably isn't for everyone). After all, these are definitions
>>   and should be as precise as possible.
>
> Reluctantly agreed. I have added all the missing "simply"s.

Good. Did you also change it for the other entailment regimes?

>> * 5.3: the "Technical Note" on not defining entailment
>>   between graphs is in fact also a Change Note, and should
>>   be marked as such in addition.
>
> It is impossible to style something both as a technical and a
> change note. In fact this is not a change, strictly speaking,
> since the text (deliberately) does not provide the definition
> (of entailment by a set of graphs) which would have been changed.

To compare the old and the new document:

The RDF 2004 Semantics, 2, explicitly talks about a "set":

     ... a set S of RDF graphs (simply) entails a graph E
     if every interpretation which satisfies every member of S
     also satisfies E.

Whereas the current working draft says:

     ... a graph G simply entails a graph E
     when every interpretation which satisfies G
     also satisfies E.

But I'm ok to have this change not explicitly marked
as a "Change Note" for the problems you were giving above.
Technically, both definitions are essentially interchangable
anyway, so the change is mainly with regard to the formulation
of the two definitions (and the current technical note
points out the only formal difference). Personally, I prefer
the new definition that only talks about a single graph more
over the set-based definition.

>> * 5.4: The Simple-semantics theorem "Every graph is
>>   satisfiable" is followed by the statement that "this
>>   does not hold for extended notions of interpretation".
>>   This text should be modified to say that it does not
>>   _always_ hold for extended notions of interpretation.
>>   One could still construct some extended notion where
>>   it does hold, although not for any of the extended
>>   notions in the RDF 1.1 Semantics.
>
> Agreed. Done.

Thanks.

>> * 5.4, Technical Note: I recommend to remove the claim about
>>   graphs containing many bnodes that this is "unlikely to
>>   occur in practice". Actually, it is relatively common,
>>   namely for OWL documents with many Boolean class expressions
>>   when serialized in RDF, because for a union or intersection
>>   class expression, the number of bnodes is proportional to the
>>   number of classes occuring in the class expression.
>>   Apart from this concrete case, an assumption of the given kind
>>   has in my opinion no place in a spec document, specifically
>>   not within a technical note.
>
> Fair point. I have also clarified the oddity of Jeremy's construction
> by changing "many bnodes" to "only bnodes".

Thanks.

>> * 7, 1st par: typos:
>>   - "... which datatype is identifier by..." should probably
>>     say "identified"
>>   - "... and should treat any literals type": probably
>>     "typed literals"
>
> Done

Thanks.

>> * 7, 2nd par: Why does the text not refer to the term
>>   "lexical space", which is introduced in the RDF 1.1 Concepts
>>   document and has been used in the original RDF Semantics
>>   (and other standards as well)? In the given form, I see no
>>   reason for the term's omission, and the text reads rather
>>   awkward without a direct reference to the lexical space.
>
> Fair point. The text is now edited to use "lexical space", as follows:
>
> A datatype is understood to define a partial mapping, called the
> <dfn>lexical-to-value mapping</dfn>, from a lexical space (a set
> of character strings) to values. The function <dfn>L2V</dfn> maps
> datatypes to their lexical-to-value mapping. A literal with
> datatype d denotes the value obtained by applying this mapping to
> the character string sss: L2V(d)(sss). If the literal string is
> not in the lexical space of the datatype, so that the lexical-to-value
> mapping gives no value for the literal string, then the literal has
> no referent.

This sounds good to me.

>> * 7, 3rd par: "RDF processors are not REQUIRED". The word
>>   "not" should also be written in uppercase to avoid
>>   misconception while reading the text.
>
> NOT REQUIRED is not an RFC 2119 defined phrase. However, after
> discussion, we have put REQUIRED itself into a non-normative lowercase.

I agree that the term is not a RFC 2119 term, and that
putting it into lowercase is thus probably the best
solution.

>> * 8: Why is there no table presenting the "RDF Vocabulary"?
>>   The RDFS chapter provides such a table, and the original
>>   RDF Semantics did so as well. It would be useful, at least.
>
> Good point. It has been added.

Thanks.

>> * Appendices: Several of the appendix titles contain the text
>>   "(Informative)", directly followed by the sentence
>>   "This section is non-normative". This is redundant. I suggest
>>   to remove "(Informative)" from the titles, in accordance
>>   with the rest of the document.
>
> This is kind of tedious, but there is a reason for it. The italicised
> sentence is added by ReSpec, but we think it desirable to have the
> table of contexts clearly indicate normativity and its lack, hence
> the inclusion of the bracketed qualifier in the section titles.
> I prefer to keep this for extreme clarity even if it is kind of silly.

Ok.

>> * Appendix D: I don't see a reason to repeat the "non-normative"
>>   declaration for the appendix in each of its sub-sections.
>
>
> ? In the version I see, they aren't so repeated.

Indeed, I now see that this was only in the original LCWD,
and there even "only" in the Reification section. It's not
in the most-current ED, so this point is indeed moot.

>> * Appendix D.2, vocabulary table: I suggest to add the additional
>>   RDFS terms for the container vocabulary as well.
>
> Good idea. Done.

Thanks.

>> * References: I do not understand why the following documents
>>   are listed as "normative references":
>>   - OWL2-SYNTAX
>>   - RDF-PLAIN-LITERAL
>
> OWL2-SYNTAX was an error, now fixed. RDF-PLAIN-LITERAL is normative
> because it is used normatively withing the document. (Section 7.)

Indeed, I missed this citation. So it is fine now.

> Please reply to public-rdf-comments@w3.org indicating whether this
> is an adequate response to your comments.

I am satisfied with all responses concerning ISSUE-166.
Please check that the explicit terminology ("RDF-entails", etc.)
is used for all regimes, not only Simple Entailment.

> Pat Hayes (for the RDF WG)

Best regards,
Michael
Received on Sunday, 27 October 2013 20:42:06 UTC

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