A reflective optical element and an EUV lithography appliance containing one such element are provided, the appliance displaying a low propensity to contamination. The nonwoven fabric has nonelastic fibers aligned in one direction and has elongation of 100% or higher in a direction perpendicular to the aligned direction of the nonelastic fibers. The present subject matter also relates to a method of synthesizing the poly. A stubification processing part 3C selects a stubification candidate file, which constitutes a target of a stubification process, in accordance with a second prescribed condition, and executes stubification processing with respect to the stubification candidate file in accordance with a third prescribed condition. The predetermined associative relationship may be preconfigured or configured by a user.