W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > November 2009

Re: URIs in @rel and @property...

From: Shane McCarron <shane@aptest.com>
Date: Tue, 17 Nov 2009 07:59:12 -0600
Message-ID: <awiycdpfrh7keluni8t8w4y5.1258466352582@email.android.com>
To: Ivan Herman <ivan@w3.org>, Niklas Lindström <lindstream@gmail.com>
Cc: Mark Birbeck <mark.birbeck@webbackplane.com>, Ben Adida <ben@adida.net>, RDFa <public-rdf-in-xhtml-tf@w3.org>
I suppose a 'should not' admonition would be harmless. 

Ivan Herman <ivan@w3.org> wrote:

>That is probably correct. It is also a very bad authoring practice...
>
>In more general terms, one could declare a number of strings as being
>off-limit for CURIE-s. But I am not sure it is worth the trouble in
>terms of usage.
>
>Ivan
>
>
>
>Niklas Lindström wrote:
>> Another point though. Isn't there a problem if prefixes are declared
>> for existing protocols?
>> 
>> When prefixes are declared for e.g.:
>> 
>>     xmlns:http="http://www.w3.org/2006/http#"
>>     xmlns:tag="http://example.org/tagging#"
>> 
>> With the proposed rules ("unsafe CURIE or URI"), wouldn't these:
>> 
>>     about="http://example.org/me"
>>     resource="tag:example.org,2009:item:1"
>> 
>> be resolved against those prefixes (instead of as-is)?
>> 
>> Best regards,
>> Niklas
>> 
>> 
>> 2009/11/16 Niklas Lindström <lindstream@gmail.com>:
>>> Ah, but indeed! Good elephant-hunting Mark! ;) It's quite comforting
>>> that RFC 3986 is so precise about these things.
>>>
>>> (I should have known that -- I now recall reading that very same rule
>>> a couple of months ago when investigating the legality of non-escaped
>>> colons in URI:s. Only remembered half of it apparently.)
>>>
>>> Best regards,
>>> Niklas
>>>
>>>
>>> 2009/11/16 Ivan Herman <ivan@w3.org>:
>>>> Pfew...:-)
>>>>
>>>> Ivan
>>>>
>>>> P.S. Mark-the-elephant-hunter:-)
>>>>
>>>> Mark Birbeck wrote:
>>>>> Hi Ivan/Niklas,
>>>>>
>>>>> 2009/11/16 Ivan Herman <ivan@w3.org>:
>>>>>> Hi Niklas,
>>>>>>
>>>>>> Niklas Lindström wrote:
>>>>>>>> So is there an elephant?:-)
>>>>>>> I haven't followed this discussion to closely, so I want to check if
>>>>>>> this the following is considered:
>>>>>>>
>>>>>>> This usage will "muddle the waters" in cases when the relative URI:s
>>>>>>> contain colon, and there is a prefix with the same name as the leading
>>>>>>> part before that, right? Concrete (but contrieved) example:
>>>>>>>
>>>>>>> Given:
>>>>>>>     - base URI: <http://en.wikipedia.org/wiki/>
>>>>>>>     - prefix Talk: <http://example.org/schema/talk#>
>>>>>>>
>>>>>>> When:
>>>>>>>     @resource="Talk:Linked_Data"
>>>>>>>
>>>>>>> Then:
>>>>>>>     - URI becomes < http://example.org/schema/talk#Linked_Data>,
>>>>>>> instead of <http://en.wikipedia.org/wiki/Talk:Linked_Data>, which is
>>>>>>> might be expected?
>>>>>>>
>>>>>> Hm. You may found the elephant:-)
>>>>>>
>>>>>> Yes, in this case one would indeed get the example.org URI.
>>>>>>
>>>>>> The question is: is this use case so strong as to nullify the advantages
>>>>>> of using CURIE-s in @about? Indeed, wikipedia uses such URI-s with ':'
>>>>>> quite a lot but the user can of course put full URI-s into the value of
>>>>>> @about...
>>>>>>
>>>>>> Thanks!
>>>>>
>>>>> Whoah...slow down. :)
>>>>>
>>>>> "Talk:Linked_Data" is not a relative path!
>>>>>
>>>>> Forget prefixes, CURIEs, whatever...even if those things did not
>>>>> exist, how would a URI processor know whether "Talk:" is a scheme or
>>>>> just part of a relative path?
>>>>>
>>>>> RFC 3986 [1] addresses this in the following way:
>>>>>
>>>>>   A path segment that contains a colon character (e.g., "this:that")
>>>>> cannot be used as the
>>>>>   first segment of a relative-path reference, as it would be mistaken
>>>>> for a scheme name.
>>>>>   Such a segment must be preceded by a dot-segment (e.g.,
>>>>> "./this:that") to make a
>>>>>   relative-path reference.
>>>>>
>>>>> So, if people are using relative paths that contain colons, in the
>>>>> wild, then there's a problem, and that problem is completely
>>>>> independent of RDFa.
>>>>>
>>>>> Regards,
>>>>>
>>>>> Mark
>>>>>
>>>>> [1] <http://www.ietf.org/rfc/rfc3986.txt>
>>>>>
>>>>> --
>>>>> Mark Birbeck, webBackplane
>>>>>
>>>>> mark.birbeck@webBackplane.com
>>>>>
>>>>> http://webBackplane.com/mark-birbeck
>>>>>
>>>>> webBackplane is a trading name of Backplane Ltd. (company number
>>>>> 05972288, registered office: 2nd Floor, 69/85 Tabernacle Street,
>>>>> London, EC2A 4RR)
>>>> --
>>>>
>>>> Ivan Herman, W3C Semantic Web Activity Lead
>>>> Home: http://www.w3.org/People/Ivan/
>>>> mobile: +31-641044153
>>>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>>>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>>>
>>>>
>
>-- 
>
>Ivan Herman, W3C Semantic Web Activity Lead
>Home: http://www.w3.org/People/Ivan/
>mobile: +31-641044153
>PGP Key: http://www.ivan-herman.net/pgpkey.html
>FOAF: http://www.ivan-herman.net/foaf.rdf
>
Received on Tuesday, 17 November 2009 13:59:48 UTC

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