A Qualitative Model of Physical Fields

A qualitative model of the spatio-temporal be-haviour of distributed parameter systems based on physical fields is presented. Field-based mod-els differ from the object-based models normally used in qualitative physics by treating parame-ters as continuous entities instead of as attributes of discrete objects. This is especially suitable for natural physical systems, e.g. in ecology. The model is divided into a static and a dynamic part. The static model describes the distribu-tion of each parameter as a qualitative physical field. Composite fields are constructed from in-tersection models of pairs of fields. The dynamic model describes processes acting on the fields, and qualitative relationships between parame-ters. Spatio-temporal behaviour is modelled by interacting temporal processes, influencing single points in space, and spatial processes that grad-ually spread temporal processes over space. We give an example of a qualitative model of a nat-ura] physical system and discuss the ambiguities that arise during simulation