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Re: ISSUE-1: Using RDF to express tokens/keywords

From: Mark Birbeck <mark.birbeck@webbackplane.com>
Date: Sun, 14 Mar 2010 21:58:43 +0000
Message-ID: <640dd5061003141458q302d2692pd7e0ce78283ac0c1@mail.gmail.com>
To: Manu Sporny <msporny@digitalbazaar.com>
Cc: RDFa WG <public-rdfa-wg@w3.org>
Hi Manu,

Great response...I agree that we're progressing. :)

I'd add a third choice though, which is the one I was inching towards
in my last email, and that is that we resolve the @token/profile issue
first, and then discuss layering a vocabulary syntax on top of that.
In other words, we do both.

First, I believe this is more correct, because ultimately what we're
creating are tokens.

The fact that tokens are generated from a vocabulary is a nice
feature, but it doesn't change what's going on -- at some point you
will end up with a value for 'name' and another for 'creator'.

So if we could agree that @token values in profiles were imported, and
that @xmlns values weren't, then we'd immediately get to first base,
and have a usable architecture that helps in an enormous number of
situations. (I realise it would need fine-tuning, but it's basically
quite simple.)

Second, my fear is that discussing a vocabulary 'syntax' could take a
loooong time; whilst it would give us great benefits once done, we'd
have missed an opportunity to hit some low-hanging fruit by delaying.
(Not sure about that metaphor...)

The reason it would take a long time is because we can't just simply
pick some predicates and declare ourselves done. Instead we'd need to
look at what else is out there and learn from it. Also, I'm pretty
certain a lot of people would have a view on what this vocabulary
syntax should look like -- rightly so -- which would also make for a
lengthy discussion.



PS I'm regretting using the term 'prefix leakage' now, after your
graphic description! :)

On Sun, Mar 14, 2010 at 9:14 PM, Manu Sporny <msporny@digitalbazaar.com> wrote:
> On 03/14/2010 08:08 AM, Mark Birbeck wrote:
>> I think you're alighting on a very small point here, when as I say,
>> the key thing is to first establish whether we should be using RDF at
>> all.
>> You seem to be implying that we *must* use RDF, because if we use
>> name/value pairs there will be 'prefix leakage'...
> Ha! I like the term 'prefix leakage' - sounds like a type of semantic
> incontinence. =P
> Background
> ----------
> Good - I think this discussion is helping. It's certainly helping me
> understand some of the more nuanced arguments that you are making as
> well as clarifying some of your goals. For example:
> * I thought you were proposing that @token/@vocab would operate exactly
>  like xmlns:, but with a different attribute value syntax. Now I know
>  that wasn't your intention.
> * I thought you were proposing JSON strictly because of the Cross-Origin
>  Resource Sharing issue, but it has more to do with name/value than it
>  does with CORS.
> * I thought you had been on the call that we discussed the "using RDF
>  to express prefixes/tokens" issue, but now that I think back, you
>  may not have been there... which is why we may have been talking
>  past each other.
> I don't mean to imply that we *must* use RDF. The 'prefix leakage' issue
> is one that I'm concerned about, but you have largely mitigated that in
> your last e-mail by saying that @token/@vocab/@whatever could be a
> better solution than xmlns: and would be processed differently to
> prevent the 'prefix leakage' issue.
> We briefly discussed whether or not it makes sense to utilize RDF to
> express prefixes/tokens/keywords and also whether it makes sense to use
> RDF to express RDFa processing instructions. IIRC, there didn't seem to
> be anyone opposed to the idea of using RDF to declare
> prefixes/tokens/keywords.
> RDF Triples Influencing RDFa Processors
> ---------------------------------------
> Historically, we have been very wary of polluting the default graph. We
> don't want leaks - we want to save ourselves from the embarrassment of
> semantic incontinence (sorry, I just couldn't resist).
> Speaking from a strictly philosophical standpoint concerning language
> design, there is no hard and fast rule stating that a language processor
> cannot be affected by the language itself. Lisp is a perfect example of
> this philosophy in action - code and data are interchangeable, the
> programmer has access to the parse trees created from the program. The
> parse trees can be modified during the operation of the program to get
> different effects. One can even create Domain Specific Languages in Lisp
> at runtime, using Lisp, to express concepts more succinctly.
> Languages can be written in the languages themselves. A language can
> have the ability to affect the runtime, which can be built into the
> language itself. C compilers, after being written in assembler, were
> then re-written in C. Javascript's prototype-based object extension
> mechanism (foo.__proto__ = proto_object) - these paradigms show that
> it's quite possible to have the interpretation of a language be
> deterministically affected by the language itself.
> We can look at this as an RDF vs. name/value discussion, but I don't
> think that's the main issue. I think the main issue has more to do with
> in-band vs. out-of-band messaging to affect how a language is interpreted.
> Two RDFa Processor Behavior Alteration Alternatives
> ---------------------------------------------------
> I could go either way on the RDF vs. name/value discussion as I have
> come to understand it over the past few days.
> 1. We choose a new attribute @token/@keyword/@whatever to add mappings
>   to the "list of mappings". That mechanism would be preferred to
>   xmlns: going forward and would operate like it, save for one
>   difference. When this new attribute is used in an RDFa Profile
>   document, the mapping would also become available in the document
>   that utilizes the RDFa Profile.
> 2. We choose to create an RDFa Processor vocabulary that could
>   future-proof us against changes to the RDFa Processor. We may or may
>   not add @token/@keyword/@whatever, but if we do, it would have
>   exactly the same functionality as @xmlns:. The RDFa Processor
>   vocabulary would have "rdfa:keyword" or "rdfa:token" or something
>   similar to provide an out-of-band mechanism of expressing mappings
>   to the RDFa Processor. These "rdfa:"-specific attributes would be
>   placed into a different graph - not the default graph.
> So, fundamentally, both approaches are perfectly workable... which is
> why this is going to be a difficult decision for the group. Our final
> choice is not going to be influenced by "Which solution is workable?",
> because both are, but rather "What gives us the greatest benefit for the
> future of the RDFa language?"
> Benefits of an RDFa Vocabulary
> ------------------------------
> There are some other future-proofing benefits of an RDFa Vocabulary,
> which may influence our decision on the final solution. One of these may
> be how to trigger new functionality in RDFa Processors.
> ISSUE-15 [3] deals with the deprecation of the @version tag. It's going
> to be a hard argument to get @version re-instated in HTML WG.
> Alternatively, we could create a new element "rdfa:version" - which
> authors could optionally use to ensure that their document is parsed
> according to a certain versions Processing rules:
> <head>
> ...
>  <meta property="rdfa:version" content="1.1" />
> ...
> </head>
> Assuming that we're going to make the default @datatype a plain literal
> in RDFa 1.1. We could do other tricks like "rdfa:default_datatype" -
> which would tell the RDFa Processor to generate XMLLiterals for elements
> that contain children if no datatype is present:
> <head>
> ...
>  <meta property="rdfa:version" content="1.1" />
>  <link rel="rdfa:default_datatype" resource="rdf:XMLLiteral" />
> ...
> </head>
> ...
> <div property="math:formula">E = mc<sup>2</sup></div>
> I'm not arguing that we want to do this... just that we /could/ do this
> if we wanted to, along with expressing tokens/keywords, without
> inventing a new attribute each time we wanted to extend the
> functionality of RDFa Processors.
> Other Factors Influencing this Decision
> ---------------------------------------
> There are a number of other questions that may better influence this
> decision - among them are:
> * Does one of these solutions solve other issues that we have
>  identified?
> * Does one of these solutions provide some degree of language
>  future-proofing?
> If we choose Solution #1 above, we may simultaneously solve ISSUE-1 [1]
> and ISSUE-14 [2].
> If we choose Solution #2 above, and with the addition of
> @token/@keyword/@whatever, we may simultaneously solve ISSUE-1,
> ISSUE-14, and ISSUE-15 [3]. We may also provide some degree of
> future-proofing for RDFa Processors.
> -- manu
> [1] http://www.w3.org/2010/02/rdfa/track/issues/1
> [2] http://www.w3.org/2010/02/rdfa/track/issues/14
> [3] http://www.w3.org/2010/02/rdfa/track/issues/15
> --
> Manu Sporny (skype: msporny, twitter: manusporny)
> President/CEO - Digital Bazaar, Inc.
> blog: PaySwarming Goes Open Source
> http://blog.digitalbazaar.com/2010/02/01/bitmunk-payswarming/
Received on Sunday, 14 March 2010 21:59:22 UTC

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