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; 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; 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; and 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; 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 a 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.