The standard provides a means to extend the N42 schema by added custom elements to selected standard N42 elements. Before adding custom elements, however, it shall be determined that there is no possibility of representing the desired data using existing N42 elements. An example of a schema with added custom elements is shown here. A complete example showing the extension of the N42 standard file for the neutron handheld instrument is provided below.
Example of an extension of the N42 standard file: http://physics.nist.gov/N42/2011/AnnexL.n42