Hi Vasiliy,

I think it comes down to the application. Whenever you dereference a URI, your application is almost certainly going to want some types of content and not others. You're bound to do various bits of sniffing and testing to see whether what you're going to get back is something you can process/use. If you follow an rdfs:seeAlso and get back something that you can use, whatever format its in, well, use it. What I'm concerned about is the implication that, S rdfs:seeAlso O implies that O is RDF that somehow doesn't need to be tested before you throw it at a parser. That seems dangerous at best.

Now, things like foaf:isPrimaryTopicOf and other predicates may well be better choices than rdfs:seeAlso for linking to non-RDF sources, but to err is human. As more people publish triples, be they in RDFa, Turtle RDF/XML or whatever, there will be errors and we'll have to handle them. What I would feel very uncomfortable with is the idea that if you include S rdfs:seeAlso O and O is not RDF then that action alone might be seen as meaning the data is invalid - which I think is way too strong an inference to make.

Phil

On 13/01/2011 11:36, Vasiliy Faronov wrote:
On Чтв, 2011-01-13 at 11:04 +0000, Phil Archer wrote:
Describing a URI with further triples is good, nothing wrong with that,
but to use that to decide whether or not to dereference an rdfs:seeAlso
URI means looking for a description of the linked resource and then
acting accordingly. That sounds like a relatively heavy bit of
processing that HTTP kind of takes care of for you.

Phil, how then do you propose to deal with the following:

- RDFa
- web servers that (in full compliance with the spec[1]) ignore the Accept
   header and just send 200 with the only representation they have (try
   HEAD http://dev.w3.org/html5/spec/Overview.html with Accept:
   application/rdf+xml, pay attention to the Content-Length returned)

[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.7


--


Phil Archer
Talis Systems Ltd
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Tel: +44 1473 434770
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