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Re: Simple Rules in Sesame

From: Holger Knublauch <holger@knublauch.com>
Date: Tue, 5 May 2009 21:05:40 -0700
Message-Id: <C368F8B4-651B-4CFC-980F-AA32EAE03D22@knublauch.com>
To: Semantic Web <semantic-web@w3.org>
> NetworkedGraphs [1, 2] are SPARQL based views / rules for RDF  
> developed at the
> University of Koblenz, similar to SPIN, but more powerful.

Hi Simon,

many thanks for creating Networked Graphs - this is great stuff, and  
serves as more evidence that SPARQL CONSTRUCT queries are an excellent  
foundation for various kinds of rules and view systems. We also align  
well with the idea of embedding SPARQL queries into RDF files.

Please allow me to respond to your statement above though, regarding  
whether NGs are "more powerful" than SPIN. This really depends on what  
aspect of SPIN you are comparing them with:

- Do Networked Graphs have the notion of constraint checking [1]?

- Do NGs have the ability to create user-defined SPARQL functions [2]  
from existing ones?

- Do NGs support something like reusable SPARQL query templates [3]?

- Do NGs allow users to define ontologies with embedded rules in an  
object-oriented style [4]?

- Are NGs supported by an enterprise-class development tool [5]?


> The implementation evaluates rules on the fly instead of  
> materializing the results.

This is an implementation detail and "SPIN" could do that too.  
Regarding the spin:rule property, SPIN simply defines a *formalism*  
for capturing such rules in a suitable place.  However, all SPIN rules  
can be made global by inserting class matching clauses that bind ?this  
into the beginning of the WHERE clause. An alternative SPIN  
implementation could take these CONSTRUCTs and push them onto the  
server for server-side evaluation, similar to what you describe in  
your Networked Graphs implementation.

Having said this, I am very interested in your work and it seems to be  
nicely complementary technology to what SPIN offers.

Regards,
Holger

[1] http://spinrdf.org/spin.html#spin-constraints
[2] http://composing-the-semantic-web.blogspot.com/2009/01/understanding-spin-functions.html
[3] http://composing-the-semantic-web.blogspot.com/2009/01/understanding-spin-templates.html
[4] http://composing-the-semantic-web.blogspot.com/2009/01/object-oriented-semantic-web-with-spin.html
[5] http://www.topquadrant.com/products/TB_Composer.html
Received on Wednesday, 6 May 2009 04:06:24 GMT

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