Re: modelling issue?

Hi Paola,

Both of these issues are covered very well in the book "Semantic Web for the
Working Ontologist: Effective Modeling in RDFS and OWL"

It is one of the books that is also available through Safari Books Online,
if you have a subscription (or sign up for a free trial) you can read it
online.

Your first issue is addressed in Chapter 6, section Modeling with Domains
and Rangers. I'm pretty sure the second issue is addressed in Chapter 3.

-Lin


On Sun, Sep 27, 2009 at 8:36 AM, Dan Brickley <danbri@danbri.org> wrote:

> On Sun, Sep 27, 2009 at 1:07 PM, Paola Di Maio <paola.dimaio@gmail.com>
> wrote:
> >
> > During Vocamp Glasgow, I tried to confront my difficulties in identifying
> > some domain range of few vocabularies that I started rdfizing as
> practice,
> > and from explosing my questions to a whole range of RDF doctors (thanks
> > Norm, Keith, Serge) two things emerged, that i did not know before
> >
> > 1) an entity (class, object, subject) does not necessarily have domain
> > /range
>
> Domain and range are characteristics of properties (aka
> relationships, attributes), rather than of the things those properties
> relate to. And yes, they're not mandatory, you can declare and use a
> property without saying anything
> about it's domain or range.
>
> The classic diagram of this (albeit for the old MCF system rather RDF,
> which was based on RDF) is
>
> http://www.w3.org/TR/NOTE-MCF-XML-970624/#sec1.2
> -> http://www.w3.org/TR/NOTE-MCF-XML-970624/simple.gif
> (minor changes: RDF has 'type' instead of 'typeOf' and today we would
> write 'author' instead of 'Author'...)
>
> > Is that so, and what's the rule/ and possibly exceptions/ that can be
> > inferred and applied?
>
> Whenever you see some property, and it has a domain of some class,
> then any use of the property can only be for saying things about an
> instance of that class. Range is the same but with the properties
> values, rather than the class the property is applied to.
>
> > that did not emerge at Vocamp
> >
> >
> > 2) Apparently a triple can be of two kinds:
> >
> > class:relation:class
> >
> >  but also
> > class:attribute:value
> >
> > Of this i would like some confirmtion (is this right?),
> > Finally,  finally, wouldnt' this ambiguity be confusing?
>
>  RDF expresses everything in terms of triples. Sometimes the triple is
> a relationship between a thing and another thing (which is often but
> not always named with a URI). And sometimes the triple is a
> relationship between a thing and a string (possibly language-tagged or
> data-typed). RDF actually calls the link in both cases a "property",
> but sometimes for communicating in other contexts you'll here
> "relation" or "relationship" (typically when the link isn't to a
> literal string value). And sometimes you will hear "attribute",
> usually when the value is a string literal.
>
> I don't think this is particularly confusing, but there is definitely
> a lot of confusion around issues like "What's the name for the set of
> things that are things that aren't strings", and "can i express
> owl:sameAs with a literal so it can be used as the subject of more
> statements". The RDF Primer might help with some or all of this... I
> haven't re-read it in a while though.
>
> > i dont have a case study for this yet, but if this is true I suspect it
> > could cause some possible  logical conflict/ambiguity
> > in semantic data model and its implementation
> > am I the only one thinking so?
>
> We had an army of logicians and mathematicians go over the 2004 specs
> in great detail. They may have missed something, but I suspect our
> main difficulties are elsewhere...
>
> > Are the above points addressed in some RDF tutorial
>
> Did you see http://www.w3.org/TR/rdf-primer/ ?
>
> cheers,
>
> Dan
>
>