[rules-users] EulerGUI released - IDE for semantic Web with Drools engine and Drools export

[Jean-Marc Vanel]

2009/2/24 Michael Zimmermann <list at incunabulum.de>

> Hi Jean-Marc,
> Jean-Marc Vanel wrote:
> ...
> > So in summary, N3 is a user-friendly language allowing to express facts,
> > class and properties, and rules.
>
> Nice to see some more work on integrating drools with the semantic web
> side. As I have worked on a related topic recently:
>
> -  Do I understand you correctly, that you use Drools as rule engine for
> rules + data where rules + data are defined in OWL?


OWL is not a language for rules, it is a language for expressing complex
class definitions, e.g; "a vegetarian pizza is a pizza whose topping has no
meat" .


> - What standard are your rules based on?

N3 logic : tutorial:  http://www.w3.org/2000/10/swap/doc/Rules ;
W3C submission: http://www.w3.org/TeamSubmission/n3/#keywords

- How capable is the OWL rules standard compared to Drools?  What do you
> think?


First the language is more compact, second you don't need to define Pojo or
any classes beforehand. Let's take an example:

@prefix : <http://exampleS.com#> .
{ ?x :parent ?y } =>  { ?y :child ?x }.

Here is the Drools translation that you can run inside EulerGUI, and export
out of it :

rule "parents.n3 0"
when
  Triple( $x : subject, predicate == "<http://exampleS.com#parent>", $y :
object )
then
  insert( new Triple( $y, "<http://exampleS.com#child>", $x ) );
end

I would say that for pure logic rules (not too many Java calls in RHS) , and
moreover if you have some RDF data to process, and OWL class and property
definitions, it makes sense to use N3 rules.

EulerGUI offers 3 rules engines. The Drools translation is still lacking
many builtin functions that the Prolog EYE engine is offering (
http://www.w3.org/TR/xpath-functions/). Also the Prolog engine is able to
express logical or (disjunction) in the RHS .
On the other hand, for rules recursively building object graphs, the prolog
engine is much too slow.

In fact you can have the best of both worlds. Suppose you have a wealth of
Drools rules, plus also some RDF data and OWL ontologies. You can export
your RDF data and OWL ontologies as Java ojects ( just one class Triple is
used).  Then you can write some Drools rules that express the relations
between the Triple objects from the RDF world and the other objects refered
to in the Drools rules.
In this scenario, it is notable that the logic of OWL and RDF Schema
(transitive property, inheritance, etc), is already expressed as N3 rules
(and hence as Drools rules ).

Hope this clarifies.
-- 
Jean-Marc Vanel
http://jmvanel.free.fr/
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