Levels of Prior Knowledge Networks
There are many different ways of representing molecular processes in a graph model. The choice of representation is often dictated by the volume of experimental data informing different parts of the model. As models increase in their level of mechanistic detail, they also decrease in the scope of the biology that they are able to cover. For example, a level 2 PPI network with hundreds of proteins may be constructed from a single co-precipitation assay, while just one relationship in a level 4 or 5 model may synthesize the results of many separate experiments. The 5 levels are expressed visually in Figure 2 and are explained in further detail below.