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

From: Ivan Herman <ivan@w3.org>
Date: Tue, 17 Nov 2009 14:40:45 +0100
Message-ID: <4B02A7DD.5080909@w3.org>
To: 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>
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 13:41:22 UTC

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