1. A method comprising accessing a first repository of metadata in a computer memory; using the first repository of metadata to set up and store a first entity-relationship diagram in a first data model in a computer memory prior to storing data values in a first database in a computer memory, wherein the first entity-relationship diagram includes a first set of data attributes stored in computer memory; using a computer processor to interpret the first entity-relationship diagram in the first data model in order to form the first database; and storing a first plurality of data records in a first database table, each including a row of a plurality of data values, in the first database; accessing a second repository of metadata in a computer memory, wherein the second repository of metadata and the first repository of metadata are substantially different; using the second repository of metadata to set up and store a second entity-relationship diagram in a second data model in a computer memory prior to storing data values in a second database in a computer memory, wherein the second entity-relationship diagram includes a second set of data attributes; using a computer processor to interpret the second entity-relationship diagram in the second data model in order to form the second database; and storing a second plurality of data records in a second database table, each including a row of a plurality of data values, in the second database; adding a first data entity and a first set of data entity relationships to the first entity-relationship diagram and storing in a computer memory; wherein the first data entity is added to the first entity-relationship diagram as an ultimate parent data entity of the first data model; wherein the first set of data entity relationships connect the first data entity to the first entity-relationship diagram; adding the first data entity and a second set of data entity relationships to the second entity-relationship diagram and storing in a computer memory; wherein the first data entity is added to the second entity-relationship diagram as an ultimate parent data entity of the second data model; wherein the second set of data entity relationships connect the first data entity to the second entity-relationship diagram; wherein an ultimate parent data entity of the first data model does not inherit any foreign key data attributes from any other data entity of the first data model, wherein a foreign key data attribute is a named data field which is used to identify a column of data values after a database has been formed and wherein a foreign key data attribute is derived from data attributes that form a unique key of a data entity; and wherein an ultimate parent data entity of the second data model does not inherit any foreign key data attributes from any other data entity of the second data model, wherein a foreign key data attribute is a named data field which is used to identify a column of data values after a database has been formed and wherein a foreign key data attribute is derived from data attributes that form unique key of a data entity; wherein the first data entity is a component of the first entity-relationship diagram which becomes a third database table in the first database, once the first database is instantiated from the first entity-relationship diagram; and wherein the first data entity is a component of the second entity-relationship diagram which becomes a fourth database table once the second database is instantiated from the second entity-relationship diagram.