importing RDF and OWL

dear all,

I added a section [1] to the RDF and OWL compatibility document about 
importing RDF/OWL and referring to the entailment regime.
I used the new two-ary Import directives in BLD:
Import(t c)
where t is the location of the RDF graph and c is the context (i.e., 
entailment regime).

Some design decisions were taken, which should be discussed in one of 
the upcoming telephone conferences.
I will briefly explain the solution that was chosen, along the lines of 
my earlier analysis of the issues:

 > Now to come back to the issue of referring to/importing RDF/OWL:
 >
 > We have two somewhat orthogonal issues:
 > a- how to refer to the RDF graph/OWL ontology
 > b- how to decide which entailment regime to use
 >
 >
 > It would of course be possible to leave both things out of RIF, but I
 > think we should at least give people the chance to refer to RDF
 > graphs/OWL ontologies.  I also have the feeling that most people in
the
 > working group would not have a problem with that.
 > First of all, the shape of such a reference would depend our earlier
 > decision between directive/syntax extension.
 >
 > Then, I see three ways to include such references:
 > 1-  use the RIF "imports" statement.  An advantage would be that we
use
 > the same key word for all things that are "imported".  A disadvantage
 > would be that the term is overloaded.
 > 2- define a new keyword, e.g. "data source reference"
 > 3- define a range of keywords, one for each entailment regime, e.g.
 > "importOWLDL", "importOWLFull"

The solution is in the end a mix between 1 and 2:
the same keyword is used for both RIF rulesets and RDF graphs, but the 
one-ary form is exclusively used for importing RIF rulesets and the 
two-ary form is exclusively used for importing RDF graphs.


 > concerning issue (b):
 > 1- If we want to include references to entailment regimes, we can
 > include a keyword "entailmentRegime", and invent IRIs for the
respective
 > entailment regimes.
 > 2- Another possibility would be to include "switches", i.e., define a
 > new keyword for each entailment regime and inclusion of such a keyword
 > would mean you want to use it.

The second argument of the import statement is used to indicate the 
entailment regime (here called "context").  Each context has an IRI.

You can find the IRIs I proposed in [1].  I tried to reuse existing IRIs 
as much as possible; in the end these are all locations of sections in 
specification documents, but I'm not sure we can do any better.
Any suggestions for better IRIs are more than welcome.

I did not want users to be required to pick a specific context, so I 
introduced two notions:
- specific contexts: the combination should be interpreted according to 
this context
- generic contexts: one can indicate whether the imported graph is 
intended to be RDF or OWL, but the user is not bound by any specific 
entailment regime, and can essentially pick to one he is able to deal with.


A large share of the text in the section is concerned with the situation 
in which multiple graphs are imported with different contexts.  I 
specified an ordering of the contexts; the combination should be 
interpreted according to the highest among all contexts, or according to 
OWL Full if there is not a single highest context.
If a generic context is used, then the user should use a context that is 
at least as high as the highest among the specific contexts.


Any and all comments on the section are welcome.


Best, Jos



[1] http://www.w3.org/2005/rules/wiki/SWC#Importing_RDF_Graphs_in_RIF
-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
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