Screenshots of MetaReg core functions. (a) The model display. In the main window, the model canvas allows dynamic model layout, model simulation and display of observations (measurements) versus predictions under a particular experiment for each of the model variables. On the right (top to bottom): satellite view of the current model, variable lookup and variable property viewer. (b) Selection of variables from a gene database (NCBI Gene or SGD). (c) Formulation of a variable's logic using the wizard. (d) The discrepancy matrix, which compares predicted and observed levels for all experiments (columns) and variables (rows). (e) A logic suggested by MetaReg's model refinement algorithm. The suggestion can be further edited by the user, and incorporated into the model.