The cornerstone of our approach to building Knowledge Systems is the assembly of knowledge bases from reusable components. Each component represents an entity, event, role or property. By instantiating and combining these components, complex representations can be built simply. For an overview of the approach, see our AAAI-97 paper ("Building Concept Representations from Reusable Components") and our K-Cap '01 paper ("A Library of Generic Concepts for Composing Knowledge Bases").