A computer-implemented method comprising: • linking first and second objects (9 1, 9 2) stored in first and second respective databases (4 1, 4 2) wherein the first object (9 1) is created by a first user (6 1) having read-and-write access to the first database and read-only access to the second database and the second object is created by a second, different user (6 2) having read-only access to the first database and read-and-write access to the second database, the first object comprising a plurality of attributes including a reference identifying the first object (9 1), wherein the linking comprises a database engine, under the control of the second user: receiving a selection linking the first and second objects (9 1, 9 2); and creating an entry (21 1) for the first object (9 1) in a look up table in the second database (4 2) using the reference, the entry including, as a first reference (22 1) identifying the first object (9 1), the reference, and a second reference (23 1) identifying the second object (9 2); so as to indicate that the second object is linked to the first object when the first object is queried, even though the second user cannot update the first object; wherein the method further comprises: • database querying, wherein the querying comprises a database engine, under the control of a user (6 1, 6 2): querying the first object (9 1) stored in the first database; obtaining the reference for the first object; searching for the entry (21 1) in the look up table using the reference; in response to finding the entry in the look up table, retrieving the second reference (23 1) identifying the second object; retrieving the second object (9 2) from the second database; and displaying the first and second objects (9 1, 9 2) on a display; so as to indicate that the second object is linked to the first object. • linking first and second objects (9 1, 9 2) stored in first and second respective databases (4 1, 4 2) wherein the first object (9 1) is created by a first user (6 1) having read-and-write access to the first database and read-only access to the second database and the second object is created by a second, different user (6 2) having read-only access to the first database and read-and-write access to the second database, the first object comprising a plurality of attributes including a reference identifying the first object (9 1), wherein the linking comprises a database engine, under the control of the second user: receiving a selection linking the first and second objects (9 1, 9 2); and creating an entry (21 1) for the first object (9 1) in a look up table in the second database (4 2) using the reference, the entry including, as a first reference (22 1) identifying the first object (9 1), the reference, and a second reference (23 1) identifying the second object (9 2); so as to indicate that the second object is linked to the first object when the first object is queried, even though the second user cannot update the first object; receiving a selection linking the first and second objects (9 1, 9 2); and creating an entry (21 1) for the first object (9 1) in a look up table in the second database (4 2) using the reference, the entry including, as a first reference (22 1) identifying the first object (9 1), the reference, and a second reference (23 1) identifying the second object (9 2); • database querying, wherein the querying comprises a database engine, under the control of a user (6 1, 6 2): querying the first object (9 1) stored in the first database; obtaining the reference for the first object; searching for the entry (21 1) in the look up table using the reference; in response to finding the entry in the look up table, retrieving the second reference (23 1) identifying the second object; retrieving the second object (9 2) from the second database; and displaying the first and second objects (9 1, 9 2) on a display; so as to indicate that the second object is linked to the first object. querying the first object (9 1) stored in the first database; obtaining the reference for the first object; searching for the entry (21 1) in the look up table using the reference; in response to finding the entry in the look up table, retrieving the second reference (23 1) identifying the second object; retrieving the second object (9 2) from the second database; and displaying the first and second objects (9 1, 9 2) on a display;