Essentially a code list is a mapping from a set of key values (elements of the code list) to actual values. Most code list will map integers to character strings, but some may map character strings to other (normally longer) character strings. <br/><br/>Code list can be used in two major ways. First they can be used to associate one sort of name or value for another, such as long names for short ones, or standard names for local ones. Second, they can be used to give local information about an implementation, such as a list of standard units, or a list of class names used, etc.<br/>