Re: Deleting subgraphs via SPARQL (illegal?)

> Remember two things here -
>
> 1) A reified statement is not the same as the corresponding statement
> made up of those three elements (subject, predicate, object).  So
> asserting something about the reified statement is not - within the
> standard rdf model - changing anything about the actual triple in the
> data store.
>

"Statement" is nicely generic, it doesnt force you to actually have the 
triple stated. What prevents you from using a subclass of statement 
which does in fact state that the triple.. is stated.
That's what we do in the rdf context toolkit [1] where we attach a 
signature with a subclass of reification which basically says "this guy 
said this, up to your trust policy to decide if its in the model or not" 
perfectly legal as nobody forces you to merge all you receive to your model.


"A reified statement is not the same as the corresponding statement
made up of those three elements" is a feature not a bug.

> 2) Many, if not most, rdf engines are going to create a bunch of
> statements that are supposed to be inferred, based on some given triple
> that is inserted into the data store.  How you you going to account for
> them?
>

You also keep the original statement. Given that by rdf semantics a 
statement is uniquely identified by subject object and predicate 
(duplicates are removed), it is not really a "duplication" of state. the 
reified version and the stated version are in fact the same if you give 
that meaning to the subclass. In case of digital signatures over Minimum 
Self Contained graphs, they are the same, if your local trust model 
trusts that person.

One question i do have is.. is it really illegal to delete triples in 
rdf? should'd a RDF model reflect a real world interpretation? if the 
world changes, should the model should change as well? I believe i was 
talking to Seaborne about this. I am puzzled :-) i too gave the 
assumption that monotonicity meant shouldt delete stuff but they seemed 
to disagree based on this issue. Clarifications anyone? :-)

Giovanni

Received on Thursday, 23 June 2005 09:10:04 UTC