On Tue, 17 Oct 2000, Aaron Swartz wrote:

> This issue is more difficult than it seems. We're making RDF assertions,
> that much is clear. The question then becomes about what. If we make them
> about items with strange IDs or URIs, the problem then becomes that while,
> we're using RDF, we're not making generically useful assertions -- an RDF
> application has to know that if:
> an assertion is made about an item
> that item has a link to a URL
> then that assertion is valid for that URL

When we are making assertions about 'items' it is fine to use the URL of
the item in the rdf:about, because we are describing a particular Web
resource at a particular URL. In this case, the rss:link property will
replicate the URL used in the rdf:about - this perfectly acceptable,
though not ideal because of the replication of the URL.

When we are making assertions about a channel things are less obvious.
In Rael's first example RSS 1.0 file at

http://meerkat.oreillynet.com/?_fl=rss10

we see

<channel rdf:about="http://meerkat.oreillynet.com/">

This looks reasonable - the URL resolves to the syndication service that
is being described. This URL is a valid value for both the rdf:about and
for the rss:link property.

In the second example at

http://www.oreillynet.com/cs/rss/print/q/32?x-ver=1.0

we see

<channel rdf:about="http://www.oreillynet.com">

I'm less convinced that this is correct. This RSS file is not a
description about the resource at that URL. For example, the title of the
resource at that URL is not 'Articles from The O'Reilly Network' as
indicated in the RDF. In this case, the URL is a valid value for the
rss:link property but not for the rdf:about.

So, what is a 'channel' anyway? What is the thing being described?

Someone suggested that the channel *is* the RSS file - and that the URL of
the RSS file should be used for the rdf:about. For example, we might see

<channel rdf:about="http://meerkat.oreillynet.com/?_fl=rss10">

(BTW, the RDF-MS Spec inidcates that this can be written as simply

<channel rdf:about="">

I think).

However, this feels pretty uncomfortable to me... what we are saying is
that 'this is a description of the RSS resource that is a description of
the RSS resource that is a description of the RSS resource' ad infinitum.

I'm confused as to whether the 'channel' is the RSS file, a particular
HTML (or other) respresentation of the RSS file (as in the first example
above) or some more abstract concept that corresponds to a particular, but
changing, collection of items.

If 'channel' is simply a collection of items, then it seems appropriate to
assign it a unique identifier, a URI that is not necessarily a URL and
that doesn't necessarily resolve to anything, and use it as the value of
rdf:about?

> The question is: How much of an issue is this? Is it a reasonable assumption
> that an RDF application using RSS would be smart enough to realize this?

Not sure what you mean here? If you mean, will an arbitrary RDF
application that doesn't have built-in understanding of RSS-specific
semantics, understand what <link> means? Then, no - probably not? I
suppose that the RSS RDFS schema definition could indicate that the
rss:link property is a subProperty of dc:relation (which I think it is)...
such that if the RDF application understood dc:relation, it would have
some understanding of rss:link ??

Andy
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