W3C home > Mailing lists > Public > public-rdfa-wg@w3.org > November 2012

Re: ISSUE-143 (Prefixes too complicated): Use of prefixes is too complicated for a Web technology [RDFa 1.1 in HTML5]

From: Shane McCarron <ahby@aptest.com>
Date: Tue, 6 Nov 2012 09:13:52 -0600
Message-ID: <CAOk_reHTeG8sQE_PYfXB+=Q7D3_Gbwi0md==-UC6ic+MN3er8A@mail.gmail.com>
To: Stéphane Corlosquet <scorlosquet@gmail.com>
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, Manu Sporny <msporny@digitalbazaar.com>, RDFa Working Group <public-rdfa-wg@w3.org>
I feel like we have addressed this concern by having nicely pre-defined
prefixes in our host language initial contexts.  It should be a reasonable

On Tue, Nov 6, 2012 at 9:06 AM, Stéphane Corlosquet

> Hi Tab,
> On Mon, Nov 5, 2012 at 7:16 PM, Tab Atkins Jr. <jackalmage@gmail.com>wrote:
>> On Wed, Oct 24, 2012 at 10:37 AM, Manu Sporny <msporny@digitalbazaar.com>
>> wrote:
>> > On 10/24/12 12:30, RDFa Working Group Issue Tracker wrote:
>> >> ISSUE-143 (Prefixes too complicated): Use of prefixes is too
>> >> complicated for a Web technology [RDFa 1.1 in HTML5]
>> >>
>> >> http://www.w3.org/2010/02/rdfa/track/issues/143
>> >
>> > Hi Tab,
>> >
>> > The RDFa WG has officially recorded your formal objection for the
>> > HTML+RDFa 1.1 specification. We're tracking it in our issue tracker now.
>> > Could you please outline one or more proposals that would result in the
>> > withdrawal of your formal objection?
>> Yes.
>> As outlined in the original threads that introduced this issue, usage
>> in the wild shows that authors very commonly author "invalid" markup
>> which uses a common prefix without specifying the prefix.  Consumers
>> have evolved to recognize these common prefixes without the
>> declaration, and in some (most?) cases may actually ignore the
>> declaration entirely and simply always assume that the common prefix
>> translates to the common URL.
>> This presents us with several problems:
>> 1. Authors appear to usually use only a handful of common prefixes,
>> and assign intrinsic meaning to these prefixes.  This suggests that
>> the indirection of prefixes may be too complex and unnecessary in the
>> first place, and we would be better served by just treating the
>> prefixes themselves as meaningful, rather than as a shortener for the
>> "real" meaningful things, the URLs.
>> 2. The developers of consumers either *also* share this
>> misunderstanding, or just don't find it worthwhile to be correct when
>> they can do just as well in practice by treating the prefix as
>> meaningful.  This suggests that there may be a real interoperability
>> danger if an author *properly* declares a prefix where the prefix is a
>> common one, but the URL is to something other than what common use
>> points to - in "correct" consumers the document will be interpreted as
>> the author intended, but in many common consumers it will instead be
>> misinterpreted to be using the common vocabulary rather than what the
>> author intended.
>> 3. In addition to the theoretical interop problem above, we have a
>> real interop problem already - many consumers will happily consume
>> pages that don't declare their prefix, as long as they use a
>> "well-known" prefix for it.  A conformant consumer, on the other hand,
>> would *not* do so, and would find no valid data on the pages.  You
>> have to reverse-engineer the web to find out which prefixes need to be
>> supported without a declaration, and what URL they should be bound to.
>>  This is an obvious failure mode of a standard.
>> There are two possible changes that would resolve my objection:
>> 1. Discover and document the common prefixes in use, define them to
>> always be bound to the URL they're commonly bound to, even without an
>> actual declaration, and don't allow them to be bound to a URL other
>> than that predefined one.
> In your suggestion above, to be crystal clear, are you implying that any
> "common" predefined prefix could not be overwritten locally? For example,
> taking 'dc' as a common prefix which is usually bound to the Dublin Core
> namespace, would this markup would be invalid then?
> <html prefix="dc: http://mynamespace.org/mydc"
> ....
> <span property="dc:customprop">value</span>
> right? or rather, you would simply ignore the override at the top?
>> 2. Drop the indirection of prefixes entirely, and simply declare that
>> prefixes themselves are meaningful.  Predefine the common prefixes in
>> use.
> what about the non-common prefixes that are either not known or existing
> yet, or too "niche" to be documented in such spec. RDFa is designed to
> allow people to define their own vocabularies, some of them might not even
> be shared publicly if say they only apply to say internal corporate schemas.
> Steph.
>> Either would be acceptable, though I greatly prefer #2.  I argue that
>> #2 is perfectly acceptable for two reasons:
>> 1. If people adopted the convention of simply using their domain name
>> (quite reasonable, I think, and likely more-or-less what people will
>> naturally use anyway), it would convey the exact same meaning and
>> uniqueness as a full URL, but with less typing - "http://foo.com" is
>> 11 characters longer than "foo".
>> 2. This does not harm the ability of generic consumers to process
>> data.  The URL that a prefix is bound to has no official meaning
>> anyway - it's solely a uniquifing mechanism - so generic consumers can
>> infer nothing from it in the general case.  They can do exactly as
>> much with a non-URL prefix.  When a consumer *does* know what the URL
>> means (it's a vocabularly it recognizes), it can do something special
>> (inferring defaults, etc.), but it can do the exact same thing when it
>> knows what a particular prefix means (which is what consumers do
>> today).
>> However, if #2 is for whatever reason unacceptable, #1 is the *bare
>> minimum* that needs to be done for the RDFa spec to document reality,
>> such that a consumer can follow the spec and reasonably expect to
>> correctly consume content already on the web.  If this is not done,
>> the RDFa spec is vastly less useful, and shouldn't be pursued.
>> ~TJ
> --
> Steph.

Shane P. McCarron
Managing Director, Applied Testing and Technology, Inc.
Received on Tuesday, 6 November 2012 15:14:20 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:05:32 UTC