This paper describes a model for spatiotemporal objects whose location is fixed, but its boundaries and properties change. We refer to these as evolving objects. We consider cases where the evolution of an object is dependent of its type and propose a rule-based approach for description of spatiotemporal object’s evolution. By developing semantics of type-based evolution, we can keep a detailed history of change. We present an example where the model is able to represent type conversions and recover the evolution history of a set of objects. The model allows answers to questions about causes of change and thus deals with cases not supported by models based on objects of a unique type.