Level of invention (or degree of inventiveness, or level of solution, or rank of solution, or rank of invention) is a relative degree of changes to the previous system (or solution) in the result of solution of (one containing a contradiction). Term was defined and introduced by TRIZ author G. S. Altshuller. After initially reviewing 200,000 patent abstracts, Altshuller selected 40,000 as representatives of high level inventive solutions. The remainder involved direct improvements easily recognized within the specialty of the system.