Embodiments of the present invention provide a database system comprising: a distributed network of servers configured to store a data graph comprising linked graph entities including semantic entities linked by directed labelled links denoting semantic relationships between pairs of linked semantic entities, and also including functional entities each representing a processing operation and being linked by directed labelled links to one or more semantic entities denoting that the processing operation is configured to access the linked semantic entities during execution of the processing operation; and a database controller comprising: a partitioning unit configured to partition the data graph into sub graphs; and a distributing unit configured to allocate each sub graph to a different server from among the distributed network of servers; wherein the partitioning unit is configured to partition the data graph in dependence upon the directed labelled links to preferentially partition linked entities into the same sub graph; and wherein the distributed network of servers are configured to store the logic required to realise each processing operation on the same server as the functional entity representing the processing operation.