A sample schema and its instances in yeast. (a) An example of a schema. Each protein in the schema has a specific feature description and each edge has a type. In this case, the schema describes Ras GTPase signaling, where small G proteins from the Ras family are regulated by GTPase activating proteins (GAPs) and Guanine nucleotide exchange factors (GEFs), and in turn regulate effector kinases, which may phosphorylate other proteins. (b) Instances of the schema in S. cerevisiae.