Defining the Complexity of an Activity

Activity recognition is a widely researched area with applications in health care, security and other domains. With each recognition system considering its own set of activities and sensors, it is difficult to compare the performance of these different systems and more importantly it makes the task of selecting an appropriate set of technologies and tools for recognizing an activity challenging. In this work-in-progress paper we attempt to characterize activities in terms of a complexity measure. We define activity complexity along three dimensions – sensing, computation and performance and illustrate different parameters that parameterize these dimensions. We look at grammars for representing activities and use grammar complexity as a measurement for activity complexity. Then we describe how these measurements can help evaluate the complexity of activities of daily living that are commonly considered by various researchers.