My doctoral research attempted to construct a formal logic of verb aspect in natural language, based on Prior's logic of tense. The resulting system, Event Logic, was initially developed in an axiomatic formulation, but was subsequently given a model-theoretic semantics too. The axiomatic formulation was presented in my book The Logic of Aspect and the model theory appears in my paper The Logic of Occurrence.
Subsequently I have investigated a wide range of temporal phenomena, in a broadly logical framework; my research has moved away from natural language towards knowledge representation issues, particularly those arising in the context of Artificial Intelligence. I have been particularly interested in the qualitative description of continuous change, and with problematic temporal phenomena such as instantaneous events and indefinitely fine intermingling (`clustered variation').
From about 1993, I have become interested in spatial and spatio-temporal knowledge representations also, and in particular in the development of an account of spatial change (e.g., movement, growth and deformation) using a combination of spatial and temporal representation systems. I have investigated the structure of qualitative state-spaces defined in terms of spatial relations such as contiguity and overlap, and the use of such structures in characterising possible sequences of events in the spatial domain.
I have investigated many different areas related to spatial and temporal knowledge representation, including discrete spaces, collective phenomena (including both natural and social groupings), and spatial change and causality (including phenomena in circumscribed domains such as networks). In addition to my work on time, space, and movement, I have subsidiary interests in non-monotonic and probabilistic reasoning, and in the philosophical issues raised by artificial intelligence and the theory of computation.
A list of publications is available.