An optional XML tag in the metadata.*.xml resource file is used to specify whether the UDA is read-only. If no read-only tag is specified, the UDA will be read-write. The XML tag is <Read-Only>. For example <Read-Only></Read-Only> or just plain <Read-Only/>. Don't forget the '/'. See the example above. The read-only tag is only for the UI element so that the user cannot modify its value.