An extensible commutation engine for formatting a command buffer in a device commanding system comprises a modifiable list of constants, each constant forming a coded representation of parameters associated with a device command; at least one existing set of instructions for formatting the command buffer in accordance with a device command; and, a modifiable mapping of each set of instructions with a corresponding constant in the modifiable list of constants. Significantly, the commutation engine is extensible to accommodate device commands having new parameters by mapping the new constant with a set of instructions according to said new parameters.