Re: Testing data consistency between graphs

> On Jan 19, 2019, at 17:01, Patrick J Hayes <phayes@ihmc.us> wrote:
> 
> 
> 
>> On Jan 18, 2019, at 5:58 PM, Austin William Wright <aaa@bzfx.net <mailto:aaa@bzfx.net>> wrote:
>> 
>> Hi SWIG,
>> 
>> I've got an application that queries statements from an RDF database, and in this process, the resulting graph might "lose" the IRI of a resource and replace it with a bnode. (Specifically, my result is an RDFa document, where an element with @typeof but no @about will produce a bnode, even if it has an IRI in my data store). I want to ensure that the data in my result graph is consistent with the data in the source graph:
>> 
>> The query result graph might only return a subset of the source data, which is legal because of the Open World Assumption.
>> 
>> And (I presume) it's legal to substitute an IRI with a bnode (in the subject & object positions). In this case, the statement is just saying "Some resource exists with the given properties" which is still a true statement.
> 
> Yes. In fact, these two changes (taking a subset, and replacing an IRI with a bnode) are exactly what is called ’simple entailment’ in the RDF specs, cf https://www.w3.org/TR/rdf11-mt/#dfn-interpolation <https://www.w3.org/TR/rdf11-mt/#dfn-interpolation>. Taken together, they preserve truth in all RDF graphs, and they are the only operations which preserve truth for /any/ RDF graph. 
> 
>> 
>> I want to test that the data in my result graph is data also present in a reference graph (my source database): that no IRIs were cast to literals, that the lang/datatype on literals is preserved, and so on.
>> 
>> Graph isomorphism doesn't suffice, because bnodes are only matched with bnodes. So first, is there a formally described function that does this? Or else, what should it be called, perhaps "consistent with”?
> 
> “simply entails” is the terminology used in the normative specification documents. 
> 
> Best wishes
> 
> Pat Hayes
> 

This is exactly what I’m looking for!

I’d read RDF Semantics a while back, I had to spend some time re-reading it and really understanding it.

Thanks!

Austin.