Re: RDFa WG telecon minutes for 2010-05-13

On May 15, 2010, at 24:32 , Ben Adida wrote:

> On 5/13/10 9:07 AM, Manu Sporny wrote:
>> NOTE: RDFa WG Members - there were a number of resolutions today
>> concerning backwards-incompatible changes.
> 
> On the resolutions covered in the telecon:
> 
> plain literals: +1
> host language for @lang: +1
> 
> 
> The other two issues could be problematic, although maybe all that's needed is a bit more specificity on error handling.
> 
> 
> 
> "When both lang and xml:lang are specified on the same element, they MUST have the same value"
> 
> I don't think we can *will* the markup to be the way we want it to be. If both @lang and @xml:lang have the same value, then that line in the spec is superfluous. If they have different values, then the spec is unhelpful in resolving the conflict. I would propose that, instead of this resolution, we specify what happens when both are defined to be different values. Does the parser blow up? Do we give priority to one of them? Do we ignore both?
> 
> 

The argument at the meeting (I think it came from Shane) was that, in general, we do not specify what an RDFa processor does in case of an invalid markup. In specific languages, like in XHTML5, this is, in fact, and invalid markup which validators should handle. I am just conveying the arguments. Reading through this again, I would be perfectly happy to say that @lang has a priority for the (X)HTML(5) cases. 

Note that there is now a separate issue on whether an RDFa processor should give error messages or not. If we decide that there are (limited) cases when an RDFa processor should give those, this may be a perfect case example for it...

> 
> 
> "For prefixes defined via xmlns: and @prefix, the prefix text should be converted to lowercase by the RDFa Processor."
> 
> So what happens in the following case:
> 
> <div xmlns:foo="http://a.com" xmlns:Foo="http://b.com">
> ...
> </div>
> 
> 
> Clearly one of these @xmlns will override the other, but which one? Is it alphabetical? I don't think we've ever defined an order for handling these @xmlns attributes, have we?

And I do not think we can. By the time any processor gets to the attributes themselves in the DOM tree, the order, afaik, is unpredictable. The only thing we can do is to add that to the list of possible errors...

> 
> 
> It probably gets more complicated with @prefix:
> 
> <div prefix="foo: http://a.com Foo: http://b.com">
> ...
> </div>

That is actually the case when we can define an order...

We did discuss at some point what is the order within a @profile for the various files, ie, left-to-right or right-to-left; this is one of our open issues:

http://www.w3.org/2010/02/rdfa/track/issues/23

I guess for the sake of consistency we should probably follow the same order whatever we decide for ISSUE-23...

Ivan

> 
> 
> Which one takes precedence here?
> 
> 
> -Ben
> 
> 
> 


----
Ivan Herman, W3C Semantic Web Activity Lead
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