This paper explores representations used to reason about objects which change over time and the processes which cause changes. Specifically, we are interested in solving a problem known as geologic interpretation. To help solve this problem, we have developed a simulation technique, which we call imagining. Imagining takes a sequence of events and simulates them by drawing diagrams. In order to do this imagining, we have developed two representations of objects, one involving histories and the other involving diagrams, and two corresponding representations of physical processes, each suited to reasoning about one of the object representations. These representations facilitate both spatial and temporal reasoning.
