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Re: Turtle syntax: Please align base URI with RFC 3986 & 3987

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Sun, 26 May 2013 15:39:56 +0100
Message-ID: <51A21EBC.8090108@epimorphics.com>
To: public-rdf-comments@w3.org
David,

Isn't that covered by:

"If the base URI is obtained from a URI reference,  ..."

The syntax has

@base IRIREF .

and the @base is no different to other URIs - it is subject to URI 
resolution.  Sec 7.2 of the Turtle spec about IRIREF.

The text inside <...> is not the exact characters to be used.

Hence, the "obtained" text applies.

@base <relURI> .

is also legal as is

@base <../sibling> .

which might be occasionally useful.

	Andy

On 26/05/13 04:03, David Booth wrote:
> AFAICT, the current Turtle syntax rules permit a base IRI
> http://www.w3.org/TR/turtle/#grammar-production-base
> to include a hash ("#"):
>
>    BASE <http://example/foo#>
>
> However, the URI specification, RFC 3986,
> http://www.ietf.org/rfc/rfc3986.txt
> in section 5.1 forbids a hash in a base URI:
>
>     "A base URI
>     must conform to the <absolute-URI> syntax rule (Section 4.3).  If the
>     base URI is obtained from a URI reference, then that reference must
>     be converted to absolute form and stripped of any fragment component
>     prior to its use as a base URI."
>
> Turtle spec section 6.3
> http://www.w3.org/TR/turtle/#sec-iri-references
> does refer to other portions of RFC 3986, but not the portion that
> requires the base URI to be an absolute URI.
>
> Please align the Turtle spec with RDF 3986 by requiring that a base URI
> be an absolute-IRI as defined in RFC 3987.
>
> I see that the SPARQL spec does explicitly say:
> http://www.w3.org/TR/sparql11-query/#iriRefs
> "Base IRIs declared with the BASE keyword must be absolute IRIs".

The section also links to 4.1.1 which discusses syntax and the process 
of getting an absolute IRI.

1.2.4 says:
The abbreviated forms (relative IRIs and prefixed names) in the SPARQL 
syntax are resolved to produce absolute IRIs.

A relative URI syntax can be given to BASE - the text is just 
emphasising that the base used to resolve is not just the characters 
inside <...>.


>
> Therefore, I suggest:
>
>   - Add the following sentence to section 6.3: "Base IRIs declared with
> the @base or BASE keyword must be absolute-IRIs as defined in RFC3987."
>
>   - Add the following comment to syntax rules 5 and 5s:
>
> [5]     base     ::=     '@base' IRIREF '.'      /* See also Sec. 6.3 */
> [5s]     sparqlBase     ::=     "BASE" IRIREF   /* See also Sec. 6.3 */
>
> Thanks,
> David
>
>
>
Received on Sunday, 26 May 2013 14:40:30 UTC

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