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Re: ISSUE-12: xs:string VS plain literals: proposed resolution

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Wed, 04 May 2011 10:08:56 -0400
Message-ID: <4DC15DF8.8010304@thefigtrees.net>
To: Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr>
CC: public-rdf-wg <public-rdf-wg@w3.org>
I'd like to understand if the proposed resolution of this issue is 
("merely") a recommendation, or is a change to RDF syntactic equality. 
In particular, will we be changing 
http://www.w3.org/TR/rdf-concepts/#section-Literal-Equality such that 
"foo" and "foo"^^xsd:string are equal literals?

Looking at this through SPARQL's eyes (as I am wont to do), one of the 
goals of this change is so that I can write:

SELECT ... { ?s :p "foo" }

and have that match whether the data that was loaded into the store was 
"foo" or "foo"^^xsd:string.

Recommending that stores canonicalize to "foo" would be one way to 
accomplish this, but only for new data. (And even then, is only a 
recommendation.) If we changed (or made a SHOULD-style change) literal 
equality, then the above query would match against :s :p 
"foo"^^xsd:string as well as :s :p "foo", which -- for me -- is the goal 
of this issue.

(SPARQL defines matching based on subgraphs, which in terms is based on 
RDF graph equivalence.)

I'm not an expert on the RDF standards documents, admittedly, so I might 
be missing something.

thanks,
Lee

On 5/4/2011 6:04 AM, Antoine Zimmermann wrote:
> Hi,
>
>
> With respect to ISSUE-12, I propose that we reformulate the resolution
> as follows:
>
> "PROPOSED: Recommend that data publishers use plain literals instead of
> xs:string typed literals and tell systems to silently convert xs:string
> literals to plain literals without language tag."
>
> In the text of the spec, we may want to add some more details, saying:
>
> "In XSD-interpretations, any xs:string-typed literal "aaa"^^xs:string is
> interpreted as the character string "aaa", that is, it is the same as
> the plain literal "aaa". Thus, to ensure a canonical form of character
> strings and better interoperability, we recommend that data publishers
> always use plain literals instead of xs:string typed literals and tell
> systems to silently convert xs:string literals to plain literals without
> language tag whenever they occur in an RDF graph."
>
>
>
> Regards,
Received on Wednesday, 4 May 2011 14:09:27 GMT

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