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[protege-owl] Free, open source Drools rule engine now supported in Protege 3.5 Alpha SWRLTab - please test it with your SWRL rule bases and SQWRL queries

Martin O'Connor martin.oconnor at
Wed Apr 4 09:49:25 PDT 2012

The 3.5 alpha release of Protege-OWL is now available on the Protege web site [1]. The main focus of the 3.5 series is 
the SWRLTab's support of the Drools rule engine, thus providing a completely free and open source solution for executing 
SWRL rules in Protege-OWL. Previously, executing SWRL rules or SQWRL queries in the SWRLTab required the use of the Jess 
rule engine, which is not open source and requires a license (though it is free for academic and U.S. government use).  
A new tab called the SWRLDroolsTab provides a graphical interface for interacting with the Drools implementation.  SQWRL 
and all existing SWRL built-in libraries are supported by the Drools implementation. The existing SWRLJessTab is still 

A major new feature is the use of OWL 2 RL-based reasoners [2] by the Jess and Drools implementations. Previously, the 
SWRLTab provided very incomplete OWL reasoning when executing SWRL rules or SQWRL queries. These reasoners are highly 
configurable via GUI-based or API-based interfaces [3].

The Jess and Drools implementations are functionally identical. For small ontologies, the Drools-based OWL 2 RL reasoner 
will typically be slightly slower than the Jess-based reasoner because of its greater startup time. However, Drools is 
typically slightly faster than Jess for the inference process itself, though the difference here is minor. By default, 
both implementations will be somewhat slower than the Jess implementation in 3.4.8 and earlier because of the more 
robust reasoning that is being performed. As mentioned, the reasoners are configurable so users may increase inference 
speeds by reducing the number of inferences being generated.

We would encourage users to try the new 3.5 alpha with their existing SWRL and SQWRL rule and query collections. Please 
post any problems to the list or send me (off-list) ontologies that I can use to replicate reported problems. Make sure 
to use the latest alpha release build (currently #644) before reporting a problem.



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