Re: {Disarmed} Re: blank nodes (once again)

FWIW, my recollection of the working group discussions followed a similar path: 
that bNodes don't fundamentally add expressive power when making assertions 
about the world.  I.e. that Skolemization achieves the same effect.  I think it 
was mainly the convenience (maybe not for logicians!) argument that carried the day.

But I do recall some discussion also about the use of RDF expressions as 
patterns, a kind of query, in which their logical interpretation might vary.  If 
that viewpoint once had any merit, I suspect it has been rather overtaken by the 
subsequent standardization of SPARQL.

I know that I find bNodes convenient when constructing RDF, but also I have 
found them problematic when implementing inference machinery (by reason of 
unclear intermediate scope boundaries).  One implemenation strategy I'd probably 
use in future is to replace all bNodes internally by some form of unique 
identifier (maybe a UUID URI), then map back to bNode when serializing a graph.

So, yes, it is then just a syntactic convenience.  But not one I'd necessarily 
choose to forego.

#g
--

Dieter Fensel wrote:
> Dear all,
> 
> I am not sure it is useful to add another comment and I also
> only partially understand the contents of the flow of emails
> on this issue. However, I will try it and risking to look like a fool.
> 
> 1) bnodes are a trick to avoid thinking about useful names
> in situations you do not really care about them
> and used f.e. in implementing lists in RDF. Obviously
> they were not really needed but make life easier.
> 
> 2) Logicans entered the place and started to interpret them as
> existential quantified variables. This is not wrong (since they
> are statements about something that exists and has a certain
> property), however, it is a somehow heavy way to interpret a
> simple syntactical short-cut.
> 
> I do not think that RDF wants to forbid to interpret them as names,
> only one does not care about the specific one. Maybe a straight-forward
> way is to think about them as unique constants, i.e., use the idea
> of skolemization. I think this is also in line with a proposal of Pat,
> a down-sized version of the Jos & Enrico paper, and in sync with
> [1].
> 
> Alternatively one may simply recommend to not using them (or to
> read these thousand emails before using them).
> 
> Obviously, I may have missed the point, I may violate the charter, and I
> should read 1000 emails more carefully.  Btw, I do not think that the
> discussion is not interesting but obviously indicates a problem.
> 
> [1] G. Yang and M. Kifer: Reasoning about Anonymous Resources
> and Meta Statements on the Semantic Web, J. Data Semantics, 2003: 69~97.
> 
> 
> 
> At 21:33 20.03.2011, Enrico Franconi wrote:
> 
>> On 18 Mar 2011, at 22:14, Pat Hayes wrote:
>>
>> > As a fallback, I am thinking of writing up a spec-like document 
>> defining 'ground RDF', to show how much simpler everything is when you 
>> don't have them. It would cover RDF, RDFS, OWL and SPARQL. What do you 
>> think?
>>
>> In [1] we have formally explored this case.
>> --e.
>>
>> [1] Jos de Bruijn, Enrico Franconi, Sergio Tessaris (2005). Logical 
>> Reconstruction of normative RDF. Proc. of the Workshosp on OWL 
>> Experiences and Directions (OWLED 2005), Galway, Ireland, November 
>> 2005. <http://www.inf.unibz.it/~franconi/papers/owled-05.pdf>
>

Received on Thursday, 24 March 2011 09:09:42 UTC