W3C home > Mailing lists > Public > public-rdf-comments@w3.org > September 2014

Re: RDF 1.1 Semantics: LV and typo

From: Patel-Schneider, Peter <Peter.Patel-Schneider@nuance.com>
Date: Wed, 24 Sep 2014 22:58:51 +0000
To: Aidan Hogan <aidhog@gmail.com>
CC: "<public-rdf-comments@w3.org>" <public-rdf-comments@w3.org>
Message-ID: <65CF5823-E991-4B8B-A002-7B206350EB7F@nuance.com>
Hi:

This is an unofficial reply.

LV is mostly around in the 1.1 semantics to provide a link back to the LV in the older semantics.  It could be removed without any trouble.

However, LV is not defined circularly.  LV is defined in terms of ICEXT, I, and rdfs:Literal.

ICEXT is defined just above, and that definition uses IEXT, I and rdf:type.

IEXT is part of every interpretation. 

I is defined in the semantic conditions for ground graphs.  For IRIs, I is defined in terms of IS, which is part of every interpretation.

So, no circularity.


Defining LV as you suggest would have some interesting consequences.   You would be able to reason that a literal value (an arbitrary element of LV) is one of the literals that you can enter.  I don't think that you can conclude anything from this in RDF, but in OWL you can. 


You should think of IC and IV simply as shorthands.  They can be replaced everywhere in the current semantics by their definitions, ICEXT(I(rdfs:Class)) and ICEXT(I(rdfs:Literal), respectively.


peter


PS:  If you want the tyop to be noticed officially you should probably send in a separate message to that effect.  


On Sep 24, 2014, at 3:20 PM, Aidan Hogan <aidhog@gmail.com>
 wrote:

> Hi folks,
> 
> Regarding the RDF 1.1 Semantics document.
> 
> 
> What is the purpose of LV? (I know there's a note in 9.1, but it's in a separate non-normative section.)
> 
> The definition:
> 
> 	LV is defined to be ICEXT(I(rdfs:Literal))
> 
> ... seems to me to be circular -- in that it defines one previously unknown quantity in terms of another previously unknown quantity -- and perhaps it's unnecessary?
> 
> Would LV be equivalent to something like:
> 
> 	{ v : there exists l s.t. IL(l) = v }
> 
> ... in which case, could ICEXT(I(rdfs:Literal)) not be equated directly with the above set as a true semantic condition, dropping LV altogether?
> 
> 	ICEXT(I(rdfs:Literal)) = { v : there exists l s.t. IL(l) = v }
> 
> (If this equality doesn't hold, I'd be interested to know why. If it does hold, it would seem a better option than introducing LV.)
> 
> 
> I have a similar issue with the definition of IC:
> 
> 	IC is defined to be ICEXT(I(rdfs:Class))
> 
> ... it does not appear to be a semantic condition but rather an extension of the notion of an interpretation with the abstract idea of a class. Not sure what I would suggest here other than to formally extend the notion of an interpretation outside of the semantic conditions? Probably this could have been built-in earlier since, e.g., RDF also has some implicit notion of classes (the class rdf:Property).
> 
> (Apologies if this has been discussed before.)
> 
> 
> Minor Typo: Alex Polleres -> Axel Polleres
> 
> Best,
> Aidan
> 
Received on Wednesday, 24 September 2014 22:59:20 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 16:59:46 UTC