Embodiments are directed to semantically navigating a data collection and to providing custom data mappings for a semantic group of data items. The choices are arranged into the cover so that each choice corresponds to one sensor in the response card when the cover is placed on the response card. 1 and 10 Jcm2, and a controllable positioner for positioning the workpiece relative to the machining beam such that an amount of energy impinging the surface to be machined is substantially constant for each unit of surface area.