13. A non-transitory a machine accessible storage medium including sequences of instructions, the sequences of instructions including instructions which when executed cause the machine to perform: identifying a semantic structure; applying a constraint for deriving a signal activity of a signal output from the semantic structure according to a characteristic of the semantic structure; and performing vectorless estimation on the semantic structure utilizing the constraint to determine the signal activity that describes a toggle rate for the signal output from the semantic structure and optimizing power for the design of the system according to the signal activity of the semantic structure by modifying one of synthesis, placement, and routing of the system on the target device.
15. The article non-transitory machine accessible storage medium of claim 13 , wherein the semantic structure is an input output protocol structure.