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- FIBO/RIF work done by Dean about a year ago. It is a proper subset of RIF, and hence conforms to a W3C standard, and can be converted into SPIN and MarkLogic rules. There is no easy way to edit/view rules in RIF. It's connection to OWL is defined in the RIF standard.
- SPIN from TopQuadrant etc. Based on SPARQL, a W3C Recommendation, but the SPIN extension is just a working note. Runs on any SPARQL-enabled triple store (that's all of the ones that are actually compliant), can be edited/viewed using TopBraid Composer. Connection to RDF/OWL is part of the spec. No translations available, but there is a command-line version that can be used for unit tests.
- SWRL available in Protege for ages. It is not a W3C standard, can be edited and viewed in Protege. Connection to OWL is part of the spec. Unit tests can be performed in Protege
- Other candidates might include Flora-2, which is what the Sunflower implementation by SRI/Quarule uses, and is also used by Benjamin Grosofs implementation. It has higher expressivity than RIF/BLD (see http://www.w3.org/TR/2013/REC-rif-bld-20130205/), and is open source, though not a standard per se. A starting point write-up on the mapping from RIF to Rulelog is available at http://ruleml.org/rif/rulelog/rif/RIF-Rulelog.html. The Sunflower implementation supports validation, has a rule editor, imports OWL as the basis for rule development, etc., and I believe the same is true / planned for the Silk-based implementation. Both use Flora-2, by Michael Kifer, described at http://flora.sourceforge.net/. There are other implementations of RuleML, such as prova, which is Adrian Paschke's implementation, which provides Reactive RuleML supportsupport – see https://prova.ws/.