OWL subset

[Peter Bruhn Andersen]

On the Apache Marmotta home page it is said that the KIWI Reasoner ‘can 
be used for expressing RDFS subclass and domain inference, as well as a 
subset of OWL semantics (the one that is most interesting’.

Is the KIWI reasoned the only reasoner used in Marmotta or are there 
other options?

Where can I find a description of the subset of OWL that is implemented?

Regards,

Peter