Re: empty prefix value

Shane McCarron wrote:
>  Actually, I think the BNF that is in there now constrains this.  They 
> are evaluated LTR and the BNF says:
> 
> NCName  <http://www.w3.org/2010/02/rdfa/sources/rdfa-core/#P_prefix>  
> ':' ' '+ xs:anyURI
> 
> So it has to be a pattern that matches an NCName, a literal colon, zero 
> or more literal spaces, and then an xs:anyURI.

just to make sure, I'm saying the problem is that an empty string is a 
valid xs:anyURI, so given two valid prefix mappings:

   ("foo" = "") and ("bar" => "@")

and given that @prefix contains a white space separated list of 
prefix-name URI pairs of the form you mention, then this must be 
serialized as:

   <div prefix="foo:  bar: @">

are you agreeing and saying that's fine, or that "" can't be used as an 
xs:anyURI with @prefix, or something else?

Cheers,

Nathan

> BNF expressions are greedy, so ' '+ will consume all consecutive 
> spaces.  We can make this more explicit - no
> problem.  But what is in there now is correct.  But if smart people miss 
> that, then we need to make it more
> obvious!
> 
> 
> 
> On 9/28/2010 2:38 PM, Nathan wrote:
>> http://www.w3.org/Bugs/Public/show_bug.cgi?id=3264#c15
>> "The ˇvalue spaceˇ of anyURI is the set of finite-length sequences of 
>> zero or more characters.."
>>
>> If this (a 0 length uri-reference as you find in href="") isn't valid 
>> for @prefix then do we need to define that in rdfa core with a note / 
>> constraint / bnf?
>>
>> Best,
>>
>> Nathan
>>
>> Shane McCarron wrote:
>>>  Actually, I think I disagree.  The first example would not match the 
>>> pattern for @prefix values. The second wouldn't either, but in some 
>>> implementations might map 'foo' to 'bar:' then not do anything with 
>>> the rest of the value.
>>>
>>> On 9/28/2010 12:32 PM, Nathan wrote:
>>>> Hi All,
>>>>
>>>> Just been working on CURIE (and prefix) resolution and realised that 
>>>> given that @prefix contains a whitespace separated list of NCName to 
>>>> xs:anyURI's then a zero length value is possible, as in:
>>>> <div prefix="foo: ">
>>>> and:
>>>> <div prefix="foo:  bar: http://example.org/o#">
>>>>
>>>> Unsure if this is an issue or not but thought it best to mention.
>>>>
>>>> Best,
>>>>
>>>> Nathan
>>>>
>>>> expanded info:
>>>>
>>>>  - @prefix = NCName ':' ' ' + xs:anyURI
>>>>  - xs:anyURI can be a URI or a URI Reference
>>>>  - URI-reference = URI / relative-ref
>>>>
>>>> relative-ref can be (amongst other things) path-empty (0-length) or 
>>>> path-noscheme, which given the (trimmed) BNF:
>>>>
>>>>   path-noscheme = segment-nz-nc *( "/" segment )
>>>>   segment-nz-nc = 1*( unreserved / pct-encoded / sub-delims / "@" )
>>>>   unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
>>>>   sub-delims    = "!" / "$" / "&" / "'" / "(" / ")"
>>>>                  / "*" / "+" / "," / ";" / "="
>>>>
>>>> means that afaict, the following is currently valid
>>>>
>>>> <div prefix="foo:  bar: @ baz: $!+~"> ...
>>>>
>>>> resulting in:
>>>>   "foo" => ""
>>>>   "bar" => "@"
>>>>   "baz" => "$!+~"
>>>>
>>>>
>>>>
>>>
>>
>

Received on Tuesday, 28 September 2010 20:04:24 UTC