Re: RDF Scoping Mechanism

+3
and thanks for all the excellent N3 work!

Kind regards,

Jos De Roo | Agfa HealthCare
Senior Researcher | HE/Advanced Clinical Applications Research
T  +32 3444 7618
http://www.agfa.com/w3c/jdroo/

Agfa HealthCare NV, Moutstraat 100, 9000 Gent, Belgium
http://www.agfa.com/healthcare




Tim Berners-Lee <timbl@w3.org> 
Sent by: semantic-web-request@w3.org
07/03/2010 02:08 PM

To
Pat Hayes <phayes@ihmc.us>
cc
Semantic Web <semantic-web@w3.org>
Subject
Re: RDF Scoping Mechanism









Pat Hayes wrote:
> It wouldn't take very much to make into full first-order logic: all it 
needs is a scoping mechanism (think graph literals in N3 or named graphs, 
or my 'surfaces' idea from the Blogic talk) and negation. Mind you, that 
scoping mechanism would drive a truck through triple-store-based 
implementations, I suspect.

Well, given that every triple store I know has a fourth component,  Often 
used to store the document it came from,  that can just allow that to 
alternatively be the id of a subgraph.  You just have to allow a subgraph 
id to fill an S or O slot and viola!

Triple store object-oriented systems typically have a "store" or "graph" 
object already. You extend the statement object you can make a graph be a 
valid holder of a S or O position.

Your parser recursively calls the document parser you already has for the 
stuff between the  { }. Same with the serializer. Code you already have. A 
lot of the code is there.


The slightly more complicated bit is when you realize that ?x variables in 
SPARQL and _:y nodes in RDF are special cases of something more general, 
and when you have nested graphs you have to be able to track within which 
scope each is quantified. So each graph also gets a list of the variables 
quantified in each way.  It is a very logical extension of what we have 
with RDF which led to N3.


>> Back to tree structures and Sexpressions, no doubt :-)
> 

(Actually I think we need to make sure that lists are first class objects 
in the implementations, so that ordered collections can be handled 
efficiently. ) 


> Obvious question, regardless of implementations, is there any chance of 
getting that scoping mechanism in to RDF through W3C to rec?
> 
> Any rough ideas how long that process may take? (I'm assuming the RDF 
Semantics are bug-less and this would just be an addition).
> 
> My logic here is that if other serializations or even something N3-like 
were to go through standardization, then work would probably have to start 
on getting said scoping mech in to RDF sooner rather than later.

Well, from the standards track point of view, one could add things 
incrementally to RDF 2.0, 2.1, etc or one could just standardize N3 as it 
is, within minimum changes, focussing on code which has been working for 
many years.  That is generally an very accepted way to make a standard. 
Get n3 1.0 nailed as a standard. Demonstrate that it can be considered a 
superset of RDF. Demonstrate its use for carrying RIF.  Standardize some 
built-in function ontologies. Set up an agenda for any later developments 
to be done after  basic N3.

Tim

> 
> Best,
> 
> Nathan
>