grammar HMKNF;

WS: [ \n\t\r]+ -> skip;

kb: (lrule | orule)*;

lrule: ((head body) | head | body) '.';
head: IDENTIFIER (',' IDENTIFIER)*;
body: ':-' (katom (',' katom)*)?;

orule: oformula '.';
oformula:
	'(' oformula ')'			# parenth
	| oatom						# literal
	| oformula '->' oformula	# imp
	| oformula '|' oformula		# disj
	| oformula '&' oformula		# conj;

katom: patom | natom;
oatom: patom | fatom;
patom: IDENTIFIER;
natom: 'not' IDENTIFIER;
fatom: '-' IDENTIFIER;

IDENTIFIER: [a-z][A-Za-z0-9]*;