Re: for telecon: ISSUE-23 @profile order

On May 26, 2010, at 11:22 , Mark Birbeck wrote:

> This all makes perfect sense. :)

Me too

Ivan

> 
> On Wed, May 26, 2010 at 9:45 AM, Toby Inkster <tai@g5n.co.uk> wrote:
>> Currently RDFa Core 1.1 says that when @profile includes multiple
>> profiles, e.g.
>> 
>>        profile="http://example.com/a http://example.net/b"
>> 
>> these are processed from left to right. This means that if a particular
>> term or prefix is defined in both profiles, then the definition in the
>> latter profile "wins".
>> 
>> If we were defining RDFa in isolation, this might make perfect sense,
>> but @profile is an attribute from HTML 4 and is (at least
>> theoretically, though often not in practise) used by microformats, so
>> we need to take into account this historical baggage.
>> 
>> HTML 4 defines @profile as a list but says that only the first URI is
>> deemed to be significant, the rest being ignored. If we make allow
>> later profiles to overrule the first profile, then this seems at odds
>> with HTML 4 - we're saying that later profiles are more significant
>> than the first.
>> 
>> XMDP, the profile format used by microformats, extends the definition
>> of @profile by saying that profiles are listed in descending
>> significance. This means that when a term is defined in two profiles,
>> the first profile wins. If we do this the other way around, it may
>> prove an annoyance for people wishing to publish hybrid
>> RDFa/microformats documents.
>> 
>> It seems apt to mention GRDDL if only in passing. In GRDDL it doesn't
>> matter which order you process profiles in. That's fine.
>> 
>> Lastly, let's think about human psychology. We tend to employ a
>> technique called cognitive frontloading - i.e. we get the most important
>> things out of the way first. That means, if there's a bunch of profiles
>> I'm going to type into a list, chances are that I'm going to type in the
>> most important ones first. Given that, it makes sense for us to
>> allow earlier profiles to override later ones.
>> 
>> So my proposal is for RDFa Core 1.1 to state that profiles are handled
>> from right to left.
>> 
>> As an aside, we may wish to mention somewhere that implementations
>> should be free to download and parse the profiles in any order, or
>> in parallel. What's important is that the terms and prefixes defined in
>> them are added to the lists of terms and prefixes in the correct order.
>> 
>> --
>> Toby A Inkster
>> <mailto:mail@tobyinkster.co.uk>
>> <http://tobyinkster.co.uk>
>> 
>> 
>> 
> 


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