A large share of the energy consumption of buildings is driven by occupancy behavior. Means to minimize this share of consumption depend upon accurate information about occupant behavior. Therefore, it is important to improve sensing systems for gathering such information. However, as research on occupancy sensing systems goes beyond basic methods, there is an increasing need for better comparison of proposed occupancy sensing systems. Developers of occupancy sensing systems are also lacking good frameworks for understanding different options when building occupancy sensing systems. This poster abstract motivates the need for working towards a better categorization framework to address both of these problems. For researchers, the categorization framework is also an aid when scoping out future research in the area of occupancy sensing systems.