1. A computer-implemented method of using a plurality of selectable database mappings, the method comprising: (a) providing a computerized stored library of a plurality of database mappings, each database mapping representing the manner in which one or more fields of one or more source databases maps to one or more fields of one or more target databases; and (b) mapping one or more source databases to one or more target databases by selecting at least one of the database mappings from the library, and using the selected database mapping or mappings to perform a mapping, wherein the mapping is performed using only the relationships defined by the selected database mapping or mappings, and without using an ontology, and wherein each database mapping in the library is separately identifiable within the library prior to being selected.