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RE: [RSS-DEV] Re: Very Simple RSS 2.0 Proposal [was: Two "beefs" with RSS 1.0]

From: Dan Brickley <danbri@w3.org>
Date: Sat, 7 Sep 2002 16:51:42 -0400 (EDT)
To: <rss-dev@yahoogroups.com>
cc: <www-archive+rss@w3.org>
Message-ID: <Pine.LNX.4.30.0209071646040.19157-100000@tux.w3.org>

On Sat, 7 Sep 2002, Ziv Caspi wrote:

> Dan Brickley wrote:
>
> [...]
> > If the RSS-DEV WG were to improve RSS 1.0's account of these issues,
> and
> > offer guidlines for producers and consumers, I could live without the
> > rdf:Seq and without document ordering carrying any meaning. But all
> the
> > time RSS feeds want to have a meaningful default ordering (which will
> > often _not_ be the same as that you'd get from ordering on date of
> item),
> > I want to be able to get this from the rdf:Seq too. Otherwise we risk
> a
> > return to RSS 0.9, where it appeared to be RDF, but critical (or in
> this
> > case, non-critical but very useful) information was only available if
> the
> > feed is processed as XML rather than RDF.
>
> I would venture an estimation that most of the RSS consumers we
> currently have actually DO process RSS feeds as XML documents rather
> than RDF, if for no other reason than that XML parsers are a widely
> available and known quantity and RDF parsers are not.

Yes, there are more XML tools than RDF. I wouldn't suggest otherwise.
>
> But even if we had available RDF processors, the question of syntax
> still seems relevant to this RDF newbie. Why is it that an RDF processor
> can preserve element order when elements are wrapped in rdf:Seq, but not
> when the elements are indicated as being ordered via an external schema
> mechanism?
>
> In other words, why can't I put in my document...
>
>   <a>
>     <b/>
>     <b/>
>     <b/>
>   </a>
>
> and then say in another schema document:
>
>   the elements //a/b form a sequence, treat them as if they children
>   of a were in a rdf:Seq element

This is an idea that many people are interested in, but it is still
largely a research issue. There are no widely used XML schema languages
that let us do this, yet. The RDF design, by separating graph abstraction
from our basic RDF/XML syntax, anticipates such developments but doesn't
require them. RDF/XML documents were made so that their meaning as a graph
was standalone self-evident, without the need to read and understand some
schema that articulated the mapping (or execute some XSLT program, for
that matter). There are some proposals (eg. 'meaning definition language /
MDL', see Google for url, which address this area, btw.


> (One obvious answer to why we might still want to indicate sequences of
> items in an RSS document explicitly rather than rely on their order is
> that we might want to have the source of the document indicate more than
> one type of ordering. This is another architecture aspect which I'm not
> talking about here.)

(yes, we could have a default order in the main Seq, represent a different
ordering in another Seq, or just have smarter clients that could order on
any property)

Dan

>
> Ziv Caspi
>   cell: +972-53-668-751
>     web: http://radio.weblogs.com/0106548/
>
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Received on Saturday, 7 September 2002 16:51:43 GMT

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