1. A data structure storing data in a computer memory, said data structure accessible by an application program being executed on a data processing system, said data structure including: a hierarchy of nodes including interior nodes and leaf nodes; node pointers connecting said nodes from parent ones of said nodes to subsidiary ones of said nodes; and a root pointer pointing to a top one of said nodes; each of said nodes characterized as having a minimum size and consistent alignment, a subsidiary node type of each of said subsidiary nodes encoded in a number of bits of respective ones of said node pointers.