This section describes the various metadata codes which are locally defined. These codes can be created or modified by any site and generally refer to information which is useful in using or interpreting the data, but not strictly necessary in order to read it.
When giving datasets to other sites, it will be advisable to forward definitions of one's local codes as well. At the very least, these may be included as comments (in COMMENT records) in the first data file of a group, or, preferably, all the lists of local code definitions can be transmitted.