SWEET ontologies are written in the OWL 1 ontology language and are publicly available at this site.

SWEET 2.0 Beta ontologies available here. SWEET 2.0 is highly modular with 4100 concepts in 125 modular ontologies organized by subject. You can view the entire concept space from an OWL tool such as Protege or SWOOP by reading in sweetAll.owl. Alternatively, these ontologies can be viewed individually, as they are arranged hierarchically by subject (see Figure below). Ontologies depicted in the center represent measurement systems, used to describe basic science processes and substances, which provide the basis for Earth system science phenomena and realms, which are used in applications.

 
Older SWEET 1.1 ontologies available here.

See our Planetary Ontologies site for sharing ontologies.