An example of the heterogeneous biological network under our function prediction framework. The node set V consists of four types, {“Human protein”, “Yeast protein”, “Mouse protein”, and “Gene Ontology term”}. The edge type set R consists of five types, {“Sequence similarity”, “Protein function annotation”,“Gene Ontology relationship”,“Experimental”, and “Co-expression”}. This HBN explicitly captures interolog and transfer of annotation through heterogeneous paths across different species.