Re: Interpretation of RDF reification

Hi Dan

Dan Brickley wrote:

> I was also thinking that, if their language allows n-ary rather than 
> binary relations, folk will doubtless start using it to decorate 
> plain RDF assertions with extra bits. "Charlie loves Mary"; but how
> much? eg:sincerity='very'; and how long eg:since='tuesday', ...
> This isn't reification, but it is a common request that surfaces in
> reification-related threads around here. 

Fair point, representing n-ary relations is very likely to be a RIF 
requirement, though reflecting such relations back into RDF is less 
certain. [*]

However, we already have the SWBP document on n-ary relations - does that 
not provide a response to such requests?

>>Note that the RIF charter does not actually call for a semantic web rule 
>>language but for a framework for interchange of rules between different 
> Yup. You've pointed out the tensions here very eloquently before. My
> view is just that there must be some point in standardising such a thing
> through the World Wide Web Consortium's SW Activity, and that a spec
> that didn't fit with the bigger SW picture would likely receive a 
> hard time in public review.

Sure, the charter is clear on the need for (some) RDF and OWL 
compatibility. My point was that it might not be "a language", it's an 
"interchange framework". Now if the framework comprises an exchange syntax 
plus some defined semantics then there's no real difference. But if the 
framework is an extensible exchange syntax with a large menu of different 
semantics options then it may be hard to regard it as "a" useful language 
in its own right.

> Let me try to be clearer.
> RDF reification, considered as a mechanism for safely storing one RDF 
> graph inside another, lacks robustness when used in systems that 
> apply OWL-sanctioned inferences to RDF data. It does this because it 
> is not designed as a container mechanism; the "inner" and "outer" graphs
> share context, such that the contents of the outer graph and inner
> graph may interact, eg. by making it impossible to tell which URIs 
> were actually used in the original reified material.

Agreed, reification isn't a way to store one quoted RDF graph inside another.

>>For a framework for describing chains of deductions, which seems to be what 
>>your example is really asking for, then you might find Inference Web 
>>That includes an (OWL) ontology for exchanging proof chains.
> Interesting, but not what I'm after.
> Going back to my example, who is screwing up?
>  - the authors of registrar-1.rdf and registrar-2.rdf ?
>  - the owners of the dc:source property?
>  - the party that suggested it is good to use dc:source with
>    rdf:Statement instances?
>  - the author of nndb-bio.rdf for sharing info about co-naming URIs 
>    via owl:sameAs?
>  - the party that publishes a reification of the registrar-*.rdf claims 
>    using rdf:Statement and dc:source
>  - the party that decides to trust that document, alongside nndb-bio.rdf 
>    and load it into an RDF store (eg. Jena)
>  - the party that decides to improve that store by adding in
>    OWL-sanctioned triples
>  - the party that writes the SPARQL query against that store, expecting it 
>    to tell them whether registrar-1.rdf mentioned charlie's URI.
> If I had to apportion blame, it would be on the last step. The query
> isn't a good query to ask. 

Well it's a failure of contract between the parties involved in the store 
and the party doing the query. But, agreed, I'd "blame" the query writer 
first :-), the store is delivering a correct answer even it wasn't the 
expected one.

However, it seems to me that the correct way to treat this on the semantic 
web requires the upper layer of the layer cake, viz the "proof" bit. 
Ideally what you want is your store service able to the both deliver the 
important result (that Charlie is married to both Mary and Alice) and 
answer a "how did you arrive at that" request (which would include the 
proof chain from the owl:sameAs referencing the source data from 
registrar-1.rdf and registrar-2.rdf).

Which is why I thought that Inference Web is relevant.

It doesn't solve the presenting symptom of how to safely quote RDF 
statements, but it at least purports [**] to address the underlying problem 
of provenance reporting.


[*] All statements on RIF in here are, of course, personal statements and 
not official statements of the RIG WG.

[**] I've not really studied it closely are am not trying to endorse it 
here [***], it's just a concrete example of a proposal at the proof layer 
which seems relevant.

[***] And if you think you are going to represent this level of qualified 
attribution in a usefully-machine-processable form in the near future then 
you are a more optimistic man than I am :-)

Received on Friday, 24 March 2006 15:51:34 UTC