SWEET ontologies are written in the OWL ontology language. OWL is an XML language being adopted as a standard by the W3C. SWEET ontologies can be viewed using a standard browser. More specialized OWL-specific tools are available such as SWOOP or Protege.

SWEET 2.0 Beta expanded ontologies available here.
SWEET 2.0 is highly modular with nearly 100 ontologies organized by subject. These ontologies can be arranged hierarchically (see below). Those depicted in the center represent measurement systems, which are used to describe basic science processes and substances, which provide the basis for Earth system science phenomena, which are used in applications.

 
SWEET 1.1 ontologies available here.

See our Planetary Ontologies site for sharing ontologies.