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Re: rdf11-concepts WD ready

From: Richard Cyganiak <richard@cyganiak.de>
Date: Tue, 6 Nov 2012 21:25:24 +0000
Cc: RDF Working Group WG <public-rdf-wg@w3.org>
Message-Id: <10242A16-E3C1-42E4-97C2-DCD21DD74F4D@cyganiak.de>
To: Pat Hayes <phayes@ihmc.us>
Pat,

Thanks for these helpful comments from back in May. Responses inline.

This was tracked under ISSUE-91, which I marked PENDINGREVIEW as I believe everything is addressed.

On 30 May 2012, at 01:06, Pat Hayes wrote:
> Reading recent posts, it occurs to me that this can be misunderstood:
> 
> "The set of nodes of an RDF graph is the set of subjects and objects of triples in the graph. Predicate IRIs /may/ also appear as nodes in the graph."
> 
> The second sentence, especially by its use of RFC2119 codeword, could be read as saying that it is OK to count predicate IRIs as nodes, which is not the intended meaning. Might be better to rephrase it something like
> 
> "It is possible for a predicate IRI to also occur as a node in the same graph."

Changed accordingly.

> 3
> 
> "bijection" seems a bit heavy-mathematical for a primer (?). Maybe spell it out in more detail?

Concepts is not a Primer. IMO, if a word is in the dictionary, and used with the dictionary definition, then it doesn't need further explanation in a specification. The first sentence of the Wikipedia entry for “bijection” is: “A bijection is a function giving an exact pairing of the elements of two sets.” This works, so I claim the text is fine.

> 3.3
> "a datatype IRI being an IRI that establishes the literal value."
> 
> Slightly misleading, could be read as saying that the datatype IRI alone determines the value. Maybe re-word like
> "a datatype IRI being an IRI that determines how the lexical form maps to the literal value."

Changed accordingly.

> 3.4 
> 
> "The blank nodes in an RDF graph are drawn from an infinite set. "
> 
> This seems a rather odd way to introduce the idea. I know it is formally correct, but it reads (to me) rather jarringly. (Which set? Why that set in particular? Etc..) 
> 
> Suggest something more like:
> 
> "A blank node is a node which has no associated information or structure. In an RDF graph, a blank node represents an 'unknown' entity which may not have a name. In the abstract syntax, we specify only that blank nodes are taken from a fixed infinite set which is disjoint from the set of all IRIs and the set of all literals."
> 
> also 3.4
> 
> "Given two blank nodes, it is possible to determine whether or not they are the same."  
> 
> Um. I know I am always being acussed of thinking like a mathematician, but this doesn't make sense as stated. If there are TWO blank nodes, then obviously they aren't the same, because if they were there would only be one of them. I know it is hard to say this without using words like "identity", so I suggest simply omitting this sentence altogether, and rephrase the paragraph as something like
> 
> "RDF makes no reference to any internal structure or syntactic form of blank nodes. A blank node is simply a node in an RDF graph which has no label or other structure relevant to its RDF role."

This section survives unchanged from the 2004 spec. I, too, am not entirely happy with it. I'll raise a separate issue for that.

> 3.5
> 
> "This transformation does not change the meaning of an RDF graph, provided that the Skolem IRIs do not occur anywhere else."
> 
> (I know we agreed on this wording long ago, but...) You might add something like 
> 
> "It does however permit the possibility of other graphs subsequently using the IRI to also refer to the same entity, which was not possible when the node was blank."

I'm a bit scared of touching anything in that section as it seems likely to open a can of worms. So I'll reply saying that the current wording sounds good enough to me; but feel free to raise an issue to propose the addition.

> 5. 
> "The lexical-to-value mapping of a datatype is a set of pairs whose first element belongs to the lexical space of the datatype, and the second element belongs to thevalue space of the datatype:
> 
> 	• Each member of the lexical space is paired with (maps to) exactly one member of the value space."
> 
> Why not bite the bullet and actually say that it is a functional mapping, or even that it is a function?  You do that for the datatype maps in 5.4 and it reads very naturally.


Done. The definition now reads:

[[
The lexical-to-value mapping of a datatype is a set of pairs whose first element belongs to the lexical space, and the second element belongs to the value space of the datatype. Each member of the lexical space is paired with exactly one value, and is a lexical representation of that value. The mapping can be seen as a function from the lexical space to the value space.
]]

Best,
Richard
Received on Tuesday, 6 November 2012 21:25:47 GMT

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