This article describes further efforts to employ the Systems Entity Structure/Model Base framework as a workable foundation for model base management in advanced simulation environments and workbenches. Such management facilities aim to provide a sharable repository of models and a means of assisting users to synthesize models to satisfy the objectives of the current study. In our approach, we view a multifaceted system as needing many models on which to base control, management, design and other interventions. These models differ in level of abstraction and in formalism. Concepts and tools are needed to organize the models into a coherent whole. This paper deals with the management of model bases using system entity structure concepts. We show how the pruning process supports reuse of previously pruned structures. Concepts of context-sensitive pruning and partitioned entity structure bases are introduced to promote model base coherence and evolvability.