The user can work on an extract at the same time as another user is working on the master or another extract. When a user works on the extract, elements are claimed to the extract in a similar way to simple multiwrite databases, so no other User can work on them. When an extract User does a SAVEWORK, the changed data will be saved to the Extract. The unchanged data will still be read via pointers back to the master DB. When appropriate, the changes made to the extract are written back to the master. Also, the extract can be updated when required with changes made to the master.