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Re: GRDDL (was: RE: Extensibility strategies)

From: Henri Sivonen <hsivonen@iki.fi>
Date: Wed, 6 Aug 2008 09:30:15 +0300
Cc: Justin James <j_james@mindspring.com>, <public-html@w3.org>
Message-Id: <6241DF67-B332-4873-9184-D74B8CAE95DC@iki.fi>
To: Toby A Inkster <tai@g5n.co.uk>

On Aug 6, 2008, at 02:07, Toby A Inkster wrote:

> On 5 Aug 2008, at 20:22, Justin James wrote:
>> * It is highly complex - Look at the diagrams on that page...  
>> anything that
>> requires that many transformations and steps is prone to failure and
>> problems. One misbehaving parser in that chain breaks it.
> Misbehaving rendering engines have been a major annoyance for  
> authors for ages, but people still use CSS. GRDDL is very much  
> simpler than CSS. (Though GRDDL makes use of XSLT which is quite  
> complex - however, many browsers do already have reasonably good  
> XSLT implementations.)

GRDDL it is a very different from CSS in a way that is crucial  
considering the question of "CSS for semantics" particularly full  

CSS doesn't throw away the original DOM. Instead, it annotates the  
document tree with properties that are updated when the DOM is updated.

GRDDL, on the other hand, transforms the original document tree into  
RDF discarding the relationship between the RDF triples and the  
original tree nodes once the transformation has completed. Also, if  
you want the RDF triples to be updated when the document tree changes,  
you need to rerun the whole transformation. Therefore, GRDDL is not  
suitable for annotating an in-browser DOM with accessibility semantics.

(ARIA annotates the DOM without a layer of indirection: the ARIA  
properties are attached directly to DOM element nodes as attributes.)

>> * HTML abuse - This seems to be predicated on abusing and mis-using  
>> HTML.
>> Maybe I am reading it wrong.
> Not sure why you think that. GRDDL has two main methods of linking  
> to a transformation from an HTML file. The first is very much like  
> CSS...
> 	To link to a stylesheet, you use:
> 	<link rel="stylesheet" href="style.css">
> 	To link to a "semantics sheet", you use:
> 	<link rel="transformation" href="semantics.xslt">

I'm not sure if abusing HTML is the right characterization, but the  
GRDDL setup violates the The Rule of Least Power TAG Finding.

Instead of serving non-scripted HTML with well-known semantics  
(<title>foo</title>) at URI u or serving some RDF triples (http://purl.org/dc/elements/1.1/title 
  of u is "foo"), GRDDL is about serving a program and a black box of  
data and telling the consumer to run the program with the data as the  
input in order to obtain RDF triples as the output of the program.

Would it be an abuse of SVG if an SVG image wasn't served directly,  
but instead a script that fetched the SVG file using XHR and rendered  
it to <canvas> was served?

Henri Sivonen
Received on Wednesday, 6 August 2008 06:30:57 UTC

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