Search Result for "negation by failure":
perl: warning: Please check that your locale settings:
	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_TIME = "tr_TR.UTF-8",
	LC_MONETARY = "tr_TR.UTF-8",
	LC_ADDRESS = "tr_TR.UTF-8",
	LC_TELEPHONE = "tr_TR.UTF-8",
	LC_NAME = "tr_TR.UTF-8",
	LC_MEASUREMENT = "tr_TR.UTF-8",
	LC_IDENTIFICATION = "tr_TR.UTF-8",
	LC_NUMERIC = "tr_TR.UTF-8",
	LC_PAPER = "tr_TR.UTF-8",
	LANG = "C"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
1 definitions retrieved:

The Free On-line Dictionary of Computing (18 March 2015):

negation by failure An extralogical feature of Prolog and other logic programming languages in which failure of unification is treated as establishing the negation of a relation. For example, if Ronald Reagan is not in our database and we asked if he was an American, Prolog would answer "no". (1994-11-29)