Re: How to represent logic expressions in RDF (issue 2)

Dear William,

>
> My apologies for being silent these past weeks, I have been 
> oversubscribed.
> Could somebody please add me on the github group so that I can comment
> on things? My username there is wwaites.

I believe that you do not need to be added to the github to be able to 
comment and add issues. You already started the very helpful list of 
implementations there without being added (here: 
https://github.com/w3c/N3/blob/master/implementations.md). Did you 
experience any problems lately?

I would like to answer the below, but maybe it makes more sense to keep 
the discussion in git?

Please let me know if you still have problems.

Kind regards,
Doerthe


>
> I was reading Issue 2 where Doerthe said that
>
>     Wikipedia says _:x. _:x a rdf:Statement…
>
> is a problem because it introduces a blank node and the reification 
> semantics
> just assert the existence of the statement, they do not assert the 
> statement.
>
> I wanted to point out that though this is true if you only consider the
>
>     _:x a rdf:Statemnet
>
> part, it is quite possible to have ’says’ govern the interpretation. 
> We can give a
> semantics of ’says’ (and abusing the notation a little) are such that,
>
>     { ?alice says ?x. ?x rdf:subject ?s; rdf:predicate ?p; rdf:object 
> ?o } =>
>     ?g { ?s ?p ?o }, ?alice says ?g.
>
> So we can get back the original bag of statements, blank nodes are not a
> problem here.
>
> More generally we can *choose* the semantics by choosing what rules to
> apply. This might be an important insight, that semantics should be as 
> far as
> possible encoded as rules which we can choose to apply or not. The reason
> that RDF reification is hard to use is that its semantics are 
> deliberatively
> underspecified — it is nearly meaningless. But we can add statements which
> use language that comes with rules to give it meaning. That’s not a 
> problem.
>
> I think we do need a syntax extension of some kind to talk about graphs
> explicitly in antecedents and consequents.
>
> I also really like the LISP proposal. It is easy to see in the rule 
> that I give
> above that we really want to be able to have nested scopes.
>
> Best wishes,
>
> William Waites | wwaites@inf.ed.ac.uk <mailto:wwaites@inf.ed.ac.uk>
> Laboratory for Foundations of Computer Science
> School of Informatics, University of Edinburgh
>
>
>
>
-- 
Dörthe Arndt
Researcher Semantic Web
imec - Ghent University - IDLab | Faculty of Engineering and Architecture | Department of Electronics and Information Systems
Technologiepark-Zwijnaarde 122, 9052 Ghent, Belgium
t: +32 9 331 49 59 | e: doerthe.arndt@ugent.be