A measuring position for finding a structural element for measuring a characteristic dimension, for instance, the critical dimension CD, which element is about to be formed on a mask, is inserted as second data information into an exchange file containing the circuit layout in a hierarchical configuration of first data information or cells representing the structural elements. To prevent the second data information, which are virtual structural elements, from being incorporated in the control instructions for mask exposure, like the first data information, as structural elements that are to be formed, the second data information does not include an allocation of a geometric shape to the measuring position, or a shape that is allocated thereto has the transparency of the background, so that there is no contrast during the exposure. The second data information can be inserted as allocated to a plane that is not converted into a control instruction.