1. One or more units of computer-readable media collectively storing a command signature data structure describing the composition of a second data structure representing a set of graphics commands, none of the units of computer-readable media being a transitory signal, the command signature data structure comprising: first information identifying a command type to which all of the graphics commands of the set correspond; and second information adequate to allow for derivation of a list of resources configured to selectively affect the outcome of graphics commands of the identified command type that are variable across the set of graphics commands, wherein the contents of the command signature data structure are usable to construct and interpret the second data structure, and wherein the second information enumerates the list of variable resources and explicitly specifies an order among them.