Go to File > Preferences > Snow Owl > Reasoners to bring up the preference page.
Snow Owl includes the following reasoner:
Reasoner
Description
An ontology reasoner with the goal of supporting the OWL 2 EL profile. Remains the world's fastest SNOMED CT classifier and is Snow Owl's default. ELK supports numerical data types.
The selected reasoner will be used for classifying SNOMED CT.
