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

Re: Prefixes fail-safe registry thoughts

From: Julian Reschke <julian.reschke@gmx.de>
Date: Tue, 03 Mar 2009 16:48:32 +0100
Message-ID: <49AD5150.6020202@gmx.de>
To: Manu Sporny <msporny@digitalbazaar.com>
CC: RDFa Developers <public-rdf-in-xhtml-tf@w3.org>, Henri Sivonen <hsivonen@iki.fi>, Ian Hickson <ian@hixie.ch>
Manu Sporny wrote:
> What follows are some thoughts about addressing some of the criticisms
> that have been raised about prefix. Specifically, those criticisms have
> been:
> 
> - Web authors don't understand indirection and will inevitably fail to
>   include prefixes in their markup.

You mean: "prefix mappings", right?

> - Prefixes are fragile under cut-paste scenarios.

Yes. So are other platform features, such as CSS.

> Henri has proposed that we get rid of CURIEs entirely and use URIs
> instead. This has a number of down-sides, authoring difficulty being the
> biggest issue. The thoughts about CURIEs are summarized on the RDFa
> wiki[1]. I believe that the RDFa TF currently does not think that this
> is an acceptable solution because of the reasons listed in [1]. Henri
> has also noted a technical issue with xmlns: in XOM.

A variation of that proposal would be to use either URIs or safeCURIEs.

> 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 adressed for @rel, because it affects 
even non-RDFa use cases.

> The biggest issue that Ian and Henri seem to have is that prefixes are
> fragile, and that they would like to not use indirection if it is at all
> possible.
> 
> So, here's something that may make both the RDFa TF and the HTML5 folks
> happy:
> 
> - 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)?

> - 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?)

> ...

BR, Julian
Received on Tuesday, 3 March 2009 15:49:22 UTC

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