As a similarity function, NICKNAME returns True if and only if both strings are non-empty and both string occur together on the same row of the ALIAS table in the DATA Directory. This function is not case sensitive. OYSTER comes with a standard table of common North American nicknames. Each row of the alias table comprises two non-empty string separated by the TAB character. Users can add or delete nickname pairs from the ALIAS table to address particular applications. If either or both strings are empty or blank, the comparator returns False. Example (using the standard table): "Robert" compared to "BOB" returns true.