The given schema suggests a global structure that can be used to accomodate the background knowledge. The extent and the organisation of this component depend on the actual implementation. For example, if one of the goals is functional classification of genes, then the Concept entity would be used to identify a gene, Term entity to store its name and aliases, while the classification hierearchy should incorporate that of gene functions. Also note that the background knowledge need not be part of the database per se, that is - it can provide the appropriate links within external resources (e.g. MIPS, SGD, GO, etc.).