>> >> Well, the RDF model theory gives a precise definition. >> In short, like any other symbol, a blank node is mapped to an element >> in the domain. Then, satisfaction of triples is determined by the >> extension function IEXT: IP -> 2^{IR x IR}. > > Interesting...this suggests that blank nodes are not treated as > variables (but as constants)? No. Both blank nodes and names are mapped to objects in the domain. The former are mapped using a blank node mapping; the second are mapped using an interpretation. > > (I ask because this is in heavy debate in the OWL WG...if RIF is going > to be playing with RDF (e.g., generalizing it) it's probably important, > or at least helpful, to coordinate. Indeed. Although, RIF does not propose to generalize RDF as such. If we merely define interoperability with respect to a superset of RDF. > >>>> The reason we consider extended RDF graphs is to accommodate >>>> possible extensions of RDF that are less restrictive in their syntax. >>> So, can we define both a general framework plus one compatibility >>> notion actually compatible with current RDF? That would be fine with me. >> >> The current notion is completely 100% compatible with standard RDF, >> since every standard RDF graph is a generalized RDF graphs, and the >> semantics is exactly the same. >> >> I just see three options: >> 1 define compatibility only with respect to standard RDF >> 2-define compatibility with respect to generalized RDF >> 3- define compatibility with respect to "semi-generalized" RDF, in >> which you would not have literals and blank nodes in property positions > [snip] > > 3 is akin to what sparql allows, yes? I guess that provides *some* reason. I guess so. Best, Jos > > Cheers, > Bijan. > -- debruijn@inf.unibz.it Jos de Bruijn, http://www.debruijn.net/ ---------------------------------------------- One man that has a mind and knows it can always beat ten men who haven't and don't. -- George Bernard Shaw
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