SUMO defines a hierarchy of classes and related rules and relationships.
Initially, SUMO was focused on meta-level concepts (general entities that do not belong to a specific problem domain), and thereby would lead naturally to a categorization scheme for encyclopedias.
To maximize compatibility, schema designers can try to assure that their naming conventions use the same meanings as SUMO for identical words (for example, "agent" or "process").
SUMO has an associated open source Sigma knowledge engineering environment.
Initially, Sumo was developed by the Teknowledge Corporation and now is maintained by Articulate Software.