Re: Comments on Last-Call Working Draft of RDF 1.1 Concepts and Abstract Syntax

On 10/19/2013 05:46 PM, Michael Schneider wrote:
> Dear Working Group!
>
> This is my review of the Last-Call Working Draft of the "RDF 1.1 
> Concepts and Abstract Syntax" specification.
>

Thank you for this careful review, Michael.   We're tracking this as 
ISSUE-161 and will respond officially in due course.

You made one point which I don't personally understand, and I'm hoping 
you can clarify/expand before the WG discusses your comments.  See below.

> Unfortunately, I only learnt about the existence of the LCWDs from 
> their announcement on the SWIG mailing list as of 3 October, with an - 
> already extended - deadline set to 17 October, which was a very short 
> time and did not give me enough time to complete the review in time. I 
> hope that you will still accept my review. I will send another review 
> for the RDF Semantics specification, which I will hopefully finish 
> till tomorrow. To ease the process for you, I have, after a mail 
> exchange with Sandro Hawke, created my review based on the 
> most-current editor drafts of the two documents:
>
> * <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html>
> * <https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-mt/index.html>
>
> I'd like to add that I have a high personal and professional stake in 
> these two documents.
>
> In general, I consider the "Concepts" document pleasing and don't have 
> any real show-stopping issues to report. Still, there are a few issues 
> that I consider "major", and a couple that I consider "minor".
>
> Major issues:
> -------------
>
> * § 3.3: "a datatype IRI, being an IRI that determines how the lexical 
> form maps to a literal value." I do not think that it is correct to 
> state that an IRIs would determine how the lexical-to-value mapping 
> works. IRIs generally do only denote some resource, in this case a 
> datatype. It's the datatype specification which determines the 
> mapping, not the IRI that denotes the datatype.
>
> * § 3.1: I believe that the "NOTE" about IRIs, literals and blank 
> nodes being distinct should be formally specified in some way, and not 
> just "noted".
>
> * § 5.1: Several of the XML datatypes listed seem to be incompatible 
> with the definition of a "lexical-to-value mapping" in the beginning 
> of §5. According to the definition, "each member of the lexical space 
> is paired with exactly one value, and is a lexical representation of 
> that value. However, for example the lexical forms of the datatype 
> "xsd:time" do not uniquely denote a single time value, but denote an 
> infinite number of recurrent time values, one per day (for a fixed 
> time zone). 

What is your source for this claim about xsd:time?     The notion that 
the lexical-to-value mapping is a function comes from XSD ("...the 
·lexical mapping· 
<http://www.w3.org/TR/xmlschema11-2/#dt-lexical-mapping> is a (total) 
function..." [1]) so I've always imagined the value space of xsd:time as 
being points on a 24-hour clock, rather than an an infinite number of 
recurrent time values.

[1]  http://www.w3.org/TR/xmlschema11-2/#lexical-space

> Further, for the datatype "xsd:date", it is not clear whether a 
> lexical form denotes a single point on the timeline (e.g. the starting 
> point of a day), or rather a whole interval of values (the whole day). 
> Variants of these problems exist for several of the other listed 
> time-related datatypes.
>

So, more broadly, it sounds like you're saying lexical mappings don't 
have to be functions, but I've always understood they did (in general) 
in both XSD and in RDF.  If I'm wrong about this, could you (1) point to 
some justification in the specs for that, and (2) explain if/why it 
matters in implementations.    That is, what code depends on whether the 
lexical mappings are or are not functions?

Thanks a lot for clarifying this.

        -- Sandro



> Minor issues:
> -------------
>
> * § 1.2, par 1, states that the term "resource" "is synonymous with 
> entity". I did not find the term "entity" being mentioned elsewhere in 
> the document, nor would I say from my experience that it is widely 
> used in the RDF world as a synonym for "resource". So I suggest to 
> remove the cited phrase.
>
> * § 1.3, 2nd item: double word: "what what"
>
> * § 3.2, the NOTE: "... that permits a much wider range...": the word 
> "much" is redundant and should in my opinion not appear in a 
> specification.
>
> * §4.1: In the introductory sentence, the two datasets D1 and D2 each 
> have only a single named graph NG1 and NG2, respectively. This would 
> be unnessesarily restrictive. Therefore, and from condition 6 of the 
> definition, I guess that NG1 and NG2 are really meant to be /sets/ of 
> named graphs for the two datatsets?
>
> * §4.1: Typos in condition 4 of the definition:
>   - comma missing in the set defining G
>   - the set defining G runs to "1n", which should be "tn" or "Tn"
>   - the set defining M(G) runs to "M(T(n))": be careful to use the same
>     term ("tn" or "Tn" that is used in the set defining G.
>
> * §5.4: "Semantic conditions of RDF MAY recognize other datatype 
> IRIs...". The term "semantic condition" is specific to the RDF Semantics
>   and as far as I can see does not appear elsewhere in the Concepts 
> document. I think that the sentence should appear only in the RDF 
> Semantics and should be removed in the Concepts document.
>
> Best regards,
> Michael Schneider
>
>
>