According to one embodiment of the present invention, a controller that partitions a media library for multiple host applications can, for each partition, assign a base element address for an element type and associate physical element addresses for elements of an element type with an index value. For a partition, the logical element address corresponding to a physical element address for an element can be determined by adding the index number associated with the physical element address to the base element address for that element type. The physical element address corresponding to a logical element address for an element can be determined by subtracting the base element address for the element type from the logical element address for the element. The result of subtracting the base element address from the logical element address is an index value for which the associated physical element address can be found.