Illustration of how the target determines the processing workflow. The two trees represent the same workflow specification when used with different targets. The ellipses represent recipes, and the arrows represent the output from one recipe that is fed to subsequent recipes. The target recipe in each case is indicated by the black outline. The ellipses for recipes that are executed are in green; non-executed recipes are in grey. The corresponding file association step is shown in Fig. 2 (see text for a detailed explanation).