NIKL was the successor to KL‐ONE, the first knowledge representation system to implement “term subsumption” semantics. The primary goals for NIKL were to improve the expressivity and efficiency of KL‐ONE. In the process of developing and using NIKL as the primary representational vehicle for several applications, important new representational needs were identified and addressed, and issues both theoretical and practical in knowledge representation were formulated. In this paper, we present the core of NIKL by way of description, examples, and a model theoretic semantics. We describe the motivations behind the major NIKL design decisions, and discuss NIKL'S capabilities and limitations as a working representation