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

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 4 May 2011 12:17:32 -0500
Cc: Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr>, public-rdf-wg <public-rdf-wg@w3.org>
Message-Id: <11570D1B-B5EA-40AF-B5E3-E780E1CFE5B9@ihmc.us>
To: Lee Feigenbaum <lee@thefigtrees.net>

On May 4, 2011, at 9:08 AM, Lee Feigenbaum wrote:

> 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.

Well, have SPARQL decide that the appropriate entailment is {xsd:string}-entailment (that is, D-entailment where D={xsd:string}), and that fixes the necessary matching. Seems to me that this is not RDF business, in fact. RDF already provides the machinery for doing this, all SPARQL has to do is use the existing RDF specs appropriately.

Pat

> 
> (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,
> 
> 

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Received on Wednesday, 4 May 2011 17:18:05 GMT

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