A data storage system for storing a number of versions of a number of objects, the versions of the objects being arranged in branch groups, wherein at least one version of at least one object defines a branch group, and wherein the versions of the objects are stored in accordance with their branch group, the system comprising an object versions table operable to include information relating to each version of each object and identifying, for each version of each object, a branch group to which the version of the object belongs and an object branches table operable to include information relating to each branch group and identifying, for each branch group, each version of each object that belongs to the branch group.