FIGURE 1 

Schematic representation of the methods currently used to model biological systems of various complexities. Many of the more sophisticated models require numerous kinetic parameters (or constraints of these parameters) and accurate measurement of the concentration of many of the biochemical species. One could imagine such models being effectively combined with experiments on relatively 'simple' systems such as bacteria and single-celled eukaryotes. In contrast, it is far harder to imagine these detailed models being effective for multicellular eukaryotes, which both have the challenge of different cell types and multiple intracellular compartments. Qualitative models seem rather more appropriate for metazoan organisms. These include Boolean models and graphical Bayesian models. In both cases, simpler and noisier data sets can be used to inform or train the models.