A data flow processing system has a plurality of processing elements and memory units. Communication amongst processing elements and amongst processing elements and memory units is facilitated by an interconnection network. Each processing element is pipelined. The system operates upon data objects known as tokens. The tokens initiate activity within the processing element pipelines. Included within the activities initiated by the tokens is execution of instructions. Operands for instructions are matched in non-associative portions of memory known as activation frames. The activation frame memory locations have a state field that indicates whether a value is present or not in the activation frame. The state field may also indicate other information about an activation frame memory location. The state field is used to determine what action is taken at an activation frame memory location when an instruction is executed. The state field also determines the scheduling of execution of instructions. Moreover, the state field may be manipulated independent of a value held at an activation frame memory location.