Re: OWL and RSS 1.0 [was: Re: RSS 1.1]

Given that only a small proportion of RSS systems are actually using
RSS as RDF, it seems an unrealistic leap from RSS
1.0-Barely-A-Data-Model to RSS 1.1-the-Description-Logic-Ontology.

Ok, maybe it's a noble cause, in a "Life and Notable Adventures of
that Renown'd Markup RSS" kind of way, but not taking into account the
situation on the Web probably won't help long-term. But I don't think
it really matters - you should be able to get the best of both worlds
by loosening up a bit.

A rough-and-ready OWL Full mapping may be of immediate use to folks
wanted to merge data from 1.0 and 1.1 sources. A tight but reduced
1.0/1.1 OWL DL mapping may be useful to working in more restricted
domains or with pre-filtered data, but I can't see it getting much in
the wild in the very near future, where there's a good chance the XML
won't even be well-formed, let alone consistent with a DL. But yeah,
let's have one of those too.

Cheers,
Danny.

On Wed, 19 Jan 2005 16:26:11 +0000, Sean B. Palmer
<[email protected]> wrote:
> 
> Leigh Dodds wrote:
> 
> > I'm disappointed that the RSS 1.1 RDF/OWL schema doesn't make any
> > reference to the RSS 1.0 classes and properties. Wouldn't this have
> > been a nice demonstration of RDF format evolution?
> 
> Christopher has already dealt with this in a practical sense, but I want
> here to deal with the underlying rationale. Sadly, any RSS 1.0 feed that
> uses images incorporates <image> as both a nodeElement and a propElt,
> which is mandated by the specification. In other words, rss:image is
> used as both a class and a property. These are disjoint in OWL DL:
> 
> [[[
> LVI, IOT, IOC, IDC, IOOP, IODP, IOAP, IOXP, IL, and IX are all pairwise
> disjoint.
> ]]] - http://www.w3.org/TR/owl-semantics/rdfs.html#5.4
> 
> But moreover they're disjoint in common sense; the RSS 1.0 schema is
> broken in this regard. So this is the main issue: that were we to
> provide relationships to RSS 1.0, we'd be providing them to an
> inconsistent schema. You don't define a bugfix release in terms of the
> specification whose bugs you're fixing!
> 
> A related issue is the use of further constructs in the RSS 1.0 schema
> (per [1]) that make it OWL Full, i.e. use of rdfs:Class:
> 
> [[[
> NOTE: owl:Class is defined as a subclass of rdfs:Class. The rationale
> for having a separate OWL class construct lies in the restrictions on
> OWL DL (and thus also on OWL Lite), which imply that not all RDFS
> classes are legal OWL DL classes. In OWL Full these restrictions do not
> exist and therefore owl:Class and rdfs:Class are equivalent in OWL Full.
> ]]] - http://www.w3.org/TR/owl-ref/#ClassDescription
> 
> Note that the RSS 1.1 ontology is in OWL Full, but that it only uses an
> OWL Full constuct in a two omittable places. After conversations with
> Joe Geldart on the matter, we decided that these constructs (the use of
> rdf:List, and one rdfs:Class elsewhere) was a beneficial restriction
> that could easily be omitted for OWL DL and OWL Lite tools.
> 
> So though the RSS 1.0 rdfs:Class issue isn't a clincher, if we were to
> declare RSS 1.1 terms as being equivalent to RSS 1.0 terms, we'd be
> binding ourselves ever more tightly to OWL Full, which is inconvenient.
> On the other hand, were we to define them as subClasses, it's possible
> that we'd find that RSS 1.0 class instances are instances of that part
> of rdfs:Class which is in the owl:complementOf owl:Class, so once again
> there's a possibility that we'd be incompatible with OWL--though we'd
> have to investigate this more carefully.
> 
> Note that my use of qualified cardinality constraints, a la DAML+OIL,
> has already been raised as a point which isn't clearly covered by the
> OWL Reference Guide: it suggests that qualified cardinalities are
> unacceptable, but Sean Bechhofer's OWL validator passes it, so we're
> unsure. We'll be changing them to unqualified cardinality constraints
> anyway since this doesn't change the intended semantic but does, as far
> as I know, make it OWL DL compatible.
> 
> We'll likely summarize these issues properly somewhere else, perhaps in
> the next draft of the specification, and ask www-rdf-logic or the
> nearest available OWL expert for more feedback.
> 
> [1] http://web.resource.org/rss/1.0/schema.rdf
> 
> --
> Sean B. Palmer, http://inamidst.com/sbp/
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 


-- 

http://dannyayers.com


 
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