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Re: Proposal for ISSUE-12, string literals

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 12 May 2011 22:32:24 +0100
Message-ID: <4DCC51E8.9040703@epimorphics.com>
To: public-rdf-wg@w3.org
generally +1


> 1. RDF Concepts puts more emphasis on the distinction between (syntactic) “literal equality” and (semantic, important for applications) “value equality”

+1 and talk about value equality in the general, not just strings.

> 2. RDF Concepts explicitly points out the specific string value equalities that already arise from RDF Semantics
> 3. RDF Concepts declares one of the string literal forms as canonical
> 4. Implementations MAY canonicalize, but don't have to

MAY is acceptable - SHOULD for strings is also good, but only MAY for 
numeric values because while it's reasonable to expect every system 
understands strings, it might not for XSD numerics.

> 5. The canonical form is plain literals.

> CHANGES TO 6.5.1 Literal Equality
> http://www.w3.org/TR/rdf-concepts/#section-Literal-Equality
>
>
> §4 Rename section to “6.5.2 Literal Equality and Canonical Forms”
>
> §5 Add to the beginning:
> “Equality of literals can be evaluated based on their syntax, or based on their value.”
>
> §6 Change “Two literals are equal …” to: “Two literals are syntactically equal …” in the current first paragraph.
>
> §7 Add to the end:
> “In application contexts, comparing the values of literals (see section 6.5.1) is usually more helpful than comparing their syntactic forms. Literals with different lexical forms and with different datatypes can have the same value. In particular:
>
> - A plain literal with lexical form aaa and no language tag has the same value as a typed literal with lexical form aaa and datatype IRI xsd:string
> - A plain literal with lexical form aaa and no language tag has the same value as a typed literal with lexical form aaa@ and datatype IRI rdf:PlainLiteral
> - A plain literal with lexical form aaa and language tag xx has the same value as a typed literal with lexical form aaa@xx and datatype IRI rdf:PlainLiteral”

http://www.w3.org/TR/rdf-plain-literal/#Syntax_for_rdf:PlainLiteral_Literals

does say that rdf:PlainLiteral will not occur "in syntaxes for RDF 
graphs" so when parsed in, ^^rdf:PlainLiteral does not occur. Talking 
about it in the section "6. Abstract *Syntax*" section is odd.

> EXTENDING THIS TO NUMERIC LITERALS???

Yes, to canonicalize numerics, but not change their datatype.

I'm unsure about the date/time datatypes because of the issue of with or 
without timezone and whether the timezone is useful information.

	Andy
Received on Thursday, 12 May 2011 21:32:54 GMT

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