Figure 2From: The BridgeDb framework: standardized access to gene, protein and metabolite identifier mapping servicesTransitive relationships between identifiers. In this diagram, two mapping sources (named A and B) are combined. Mapping source A defines relations between Ensembl and Entrez genes. Mapping source B is a custom microarray annotation that provides mappings between custom identifiers and Entrez. Through transitivity, the relation between the custom microarray and Ensembl can be inferred. The custom annotation file needs to define only a subset of relations.Back to article page