Assumption analysis and tracking plays a fundamental role inmodel-based Automatic Target Recognition (ATR) design and evaluation. Simply put, an Assumption Truth Maintenance System (ATMS) provides a mechanism for tracking assumptions and logical propositions, and recognizing contradictions. We propose to implement an ATMS variant, a Belief Maintenance System (BMS) as an evidence accumulation module available to model-based pattern recognition algorithms. The BMS will allow evidence accumulation within a single algorithm as well as evidence combination for complementary algorithms operating in parallel. The BMS will take the form of a software library to be used in the Center for Night Vision's MAXIMIZE system. The proposed Phase II system will expand the capabilities of the Phase I demonstrator and be integrated into MAXIMIZE.