Abstract: A data processing system comprises a number of processing nodes, each having a processor and a local store. The workload of the system is represented by packets, including function packets specifying a function and pointers to one or more argument packets to which the function is to be applied. When a node processes a function packet, it checks whether all its argument packets are resident in the local store. If not, copies of the argument packets are fetched from the remote nodes in which they reside. These argument packets are referenced by special indirection packets, which contain the local and global address of the argument packet, and a reference count for garbage collection purposes.