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Re: Turtle: Prefixes now can contain colons (":")?

From: Jan Wielemaker <J.Wielemaker@vu.nl>
Date: Tue, 17 Jul 2012 09:30:01 +0200
Message-ID: <50051479.7090907@vu.nl>
To: Mathias Hasselmann <mathias@taschenorakel.de>
CC: Gavin Carothers <gavin@carothers.name>, <public-rdf-comments@w3.org>
On 07/17/2012 09:22 AM, Mathias Hasselmann wrote:
> Am Montag, den 16.07.2012, 20:43 -0700 schrieb Gavin Carothers:
>> On Sat, Jul 14, 2012 at 1:40 PM, Mathias Hasselmann
>> <mathias@taschenorakel.de> wrote:
>>> Hello,
>>>
>>> When adopting code for the updated grammar I've noticed that that
>>> addition of colons to local names also injected colons to PN_PREFIX:
>>>
>>> http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-turtle/index.html#grammar-production-PN_PREFIX
>>>
>>> [167s]  PN_PREFIX       ::=     PN_CHARS_BASE ((PN_CHARS | '.')* PN_CHARS)?
>>> [166s]  PN_CHARS        ::=     PN_CHARS_U | '-' | [0-9] | #00B7 | [#0300-#036F] | [#203F-#2040]
>>> [164s]  PN_CHARS_U      ::=     PN_CHARS_BASE | '_' | ':'
>>>                                                       ^^^^^
>>> Is that intentional?
>>
>> Yes.
>> http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-turtle/index.html#sec-changelog
>>
>> The other major grammar addition is the support for PREFIX (without
>> the @) as seen in SPARQL.
>
> Sure, it says: "Local part of prefix names can now include ":"".
> But the way I understand the sentence this is about the local part, not
> the prefix name itself. Am I missing something.
>
> To illustrate the problem consider this prefixed name:
>
> 	abc:def:ghi
>
> What part is the prefix, what part is the local name? Especially if the
> document also contains this directives:
>
> 	@prefix abc: "http://www.example.com/first"
> 	@prefix abc:def: "http://www.example.com/second"
>
> Not saying this is impossible to implement, but I expect unnecessarily
> inefficient implementations, and also interoperability issues by
> allowing colons in the prefix name. What's actually the use case for
> permitting colons in the prefix name?

I don't know.  : already has an important role in our syntax, both for
Turtle itself as for URIs.  : is AFAIK, not a commonly used separator,
also because it is not allowed in e.g., file-names if you want
portability.  Please do not allow for : in Turtle identifiers.

	--- Jan
Received on Thursday, 19 July 2012 13:31:48 UTC

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