Figure 2.

Hairballs are composed of nodes and edges. With nodes (blue) standing for elements such as genes, proteins, or metabolites, and edges (brown) standing for qualitative or quantitative relationships, hairballs are graphical representations of explicit models. Hairballs can also represent the act of modeling itself, with nodes that represent knowledge, and edges that represent the connections models build between bodies of knowledge.

Lander BMC Biology 2010 8:40   doi:10.1186/1741-7007-8-40
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