Modelling and simulation software to support individual-based ecological modelling

Individual-based modelling is a reductionistic technique for describing ecological systems. In contrast to more traditional mathematical models, an individual-based model is not described ‘top-down’, like a black box, but ‘bottom-up’ by the structure and dynamics of the discrete entities of the system considered important for the issue under study. The majority of individual-based models are hand-coded software programs, designed and implemented by ecologists. In truth individual-based models are currently synonymous with their implementation on computer—for generally speaking no complete description of a model other than the executable program itself is available. This leads to a number of fundamental and technical problems, which may partly be overcome by the use of appropriate software tools. But although software tools are available for simulation studies in many other fields of application, the number of tools which assist individual-based modelling and simulation is limited. In this paper we examine different strategies for the software support of individual-based modelling. We identify three different layers of software support. Firstly, we discuss software frameworks being implemented on top of general purpose programming languages. Although software frameworks support the programming of any individual-based model, they can only be used by an ecologist able to develop computer programs. Secondly, we look at interactive modelling tools being used by ecologists who build models for specific fields of application. Thirdly, we investigate simulators which support users who do not want to build their own model but would rather use a predefined existing model. For each of these categories we briefly describe a tool that has been or is currently being developed at the OFFIS institute. Attention is mainly focused on the conception of a modelling tool (wesp-tool) designed to support the modelling and analysis of individual-based metapopulation models.