et" in its purely extensional sense, as
    in "naive" set theory and its more axiomatized versions.

 2. Do not use the word "class" as a technical word in KIF
    or the SUO.     

 3. Select some term from the set {"type", "sort", "category"),
    and use it for both the KIF sorts and the things in the
    SUO hierarchy.

 4. Define a denotation operator, which for any domain of
    discourse, maps the things in point #3 to sets.

 5. Avoid making a commitment whether the things mentioned
    in point #3