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

Re: Prefixes fail-safe registry thoughts

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Tue, 03 Mar 2009 11:29:19 -0500
Message-ID: <49AD5ADF.10207@digitalbazaar.com>
To: RDFa Developers <public-rdf-in-xhtml-tf@w3.org>
CC: Henri Sivonen <hsivonen@iki.fi>, Ian Hickson <ian@hixie.ch>
Julian Reschke wrote:
>> - Web authors don't understand indirection and will inevitably fail to
>>   include prefixes in their markup.
> You mean: "prefix mappings", right?

Yes, sorry, I mean "prefix mappings".

>> A number of people have proposed that instead of declaring prefixes
>> using @prefix or via @profile, that a global registry is created for
>> prefix declarations. The registry document must be fetched in order to
>> understand the prefix mapping. The issues associated with this approach
>> are listed on the rdfa wiki[2].
>> The biggest issue that the RDFa TF is interested in not creating is a
>> backward-compatibility nightmare. If RDFa is parsed differently in HTML5
>> vs. XHTML1.1, the parser code will require a number of really nasty
>> if(xhtml_flag), if(!html5) branches. Henri has noted this as an issue as
>> well.
> Indeed.
> Minimally, this issue should be addressed for @rel, because it affects
> even non-RDFa use cases.

Do you think that this proposal could address your issue with @rel?

>> - The current RDFa parsing rules don't change for XHTML. In addition,
>>   only @prefix should be used in HTML5/XHTML5. This should make the RDFa
>>   TF happy.
> But that does change the rules for XHTML, doesn't it? Or are you saying
> that XHTML != XHTML5 (== HTML5 serialized as XML)?

Not speaking as a member of the RDFa TF... just kicking around some ideas...

Yes, it does change the rules slightly, but shouldn't create any
backwards-incompatible changes. That's what I should have said:

"The @prefix addition would not create any backwards-incompatible
issues, nor would it adversely affect the processing rules. All of the
'XHTML+RDFa 1.0' documents would continue to work."

The addition of @prefix /could/ happen in the next revision of RDFa,
which would create a new mapping mechanism (not saying that it's going
to happen, just that it is a potential avenue). It could also be done in
the CURIE spec.

I was saying that XHTML1.1 != XHTML5, although we would still need to
have that discussion. My preference at this point is to phase use of
"xmlns:" out for declaring prefix mappings across all HTML family
languages, but the XML community might disagree very strongly. If there
is enough push-back, we may end up with both @prefix and @xmlns: being
acceptable in both XHTML1.1 and XHTML5, with only @prefix being
acceptable in HTML4/HTML5.

>> - If a parser detects an undefined prefix, it MAY load a prefix mapping
>>   document located at this URL:
>>      http://purl.org/rdf-prefixes/well-known-prefixes
>>   The document could be generated from the list defined at
>>   http://prefix.cc/ - perhaps, prefix.cc could be used as the definitive
>>   list? This will hopefully make the anti-prefix/anti-indirection people
>>   happy.
> On the other hand, it will make the owners of purl.org extremely
> unhappy, unless it doesn't happen frequently. (Did you talk to them?)

If the anti-indirection crowd is correct, it will happen quite
frequently. If the pro-indirection crowd is correct, it will happen
infrequently. We should plan for the worst.

I used purl.org as an example - any redirection service would do.  I
haven't talked to the purl.org folks yet - don't know who to contact
there. I also need to talk to them about http://purl.org/media# not
resolving, but http://purl.org/media/# resolving. Do you know who I
should talk to?

-- manu

Manu Sporny
President/CEO - Digital Bazaar, Inc.
Scaling Web Services past 100,000 Simultaneous Connections
Received on Tuesday, 3 March 2009 16:29:57 UTC

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