Ontology concerns itself with the representation of the objects in the
universe and the web of their various connections.  The traditional task
of ontologists has been to extract from this tangle a single ordered
structure, in the form of a tree or lattice.  This structure consists of
the terms that represent the objects, and the relationships that
represent connections between objects.  Recent work in ontology goes so
far as to consider several distinct, superimposed structures, which each
represent a classification of the universe according to a particular
criterion.

Our purpose is to defer the task of globally classifying terms and
relationships.  Instead, we focus on composing them for use as we need
them.  We define contexts to be our unit of encapsulation for ontologies,
and use a rule-based algebra to compose novel ontological structures
within them.  We separate context from concept, the unit of ontological
abstraction. Also, we distinguish composition from subsumption,
or containment, the relationships which commonly provide structure to
ontologies.  Adding a formal notion of encapsulation and composition
to ontologies leads to more dynamic and maintainable structures, and,
we believe, greater computational efficiency for knowledge bases.