Model: Feature+;
Feature: 
       {Root_Feature} 'root' name=ID '{' bodyItems+=Feature_Body_Item+ '}'	
     | ref=[Hierarchical_Feature] '{' bodyItems+=Feature_Body_Item+ '}';

Feature_Body_Item:
	| Attribute
	| Feature_Group;

Feature_Group:
	'group' '{' sub_features+=Hierarchical_Feature (',' sub_features+=Hierarchical_Feature)* '}';

Hierarchical_Feature:
	    optional?=('opt')? name=ID ('{' bodyItems+=Feature_Body_Item+'}')?;

Expression12 returns ComplexExpression: 
	Expression11 ({If.left=current} '?' right+=Expression12':' right+=Expression11)*;

Expression11  returns ComplexExpression: 
	Expression10 ({LeftImplication.left=current}'<-' right=Expression10)*;

Expression10  returns ComplexExpression:
	Expression9 ({RightImplication.right=current}'->' left=Expression9)*;

Expression9  returns ComplexExpression:
	Expression8 ({BiImplication.left=current}'<->' right=Expression8)*;

Expression8  returns ComplexExpression:
	Expression7 ({Or.right=current}'||' left=Expression7)*;

Expression7  returns ComplexExpression:
	Expression6 ({And.right=current}'&&' left=Expression6)?;

Expression6  returns ComplexExpression:
	  Expression5 (((({Equality.left=current}'==' | {Inequality.left=current}'!=') right=Expression5) | ({In.left=current}'!=')'in' right=Set_Expression))?;

Expression5  returns ComplexExpression:
	Expression4 =>(({Less.left=current} '<'=>({Lessequal.left=current} '=')?|{Greater.left=current} '>'=>({Greaterequal.left=current} '=')?) right=Expression4)?;

Expression4  returns ComplexExpression:
	Expression3 (({Plus.right=current}'+'| {Minus.right=current}'-') left=Expression3)?;

Expression3  returns ComplexExpression:
	Expression2 (({Multiplication.right=current}'*'| {Division.right=current}'/') left=Expression2)?;

Expression2 returns ComplexExpression:
	Expression (({Excludes.left=current}'excludes' | {Requires.left=current}'requires') right=Expression)?;



Expression:
	  op='!' expression=Expression12
	| op='-' expression=Expression12
	| op='(' expression=Expression12 ')'
	| op='abs' '(' expression=Expression12')'
	| op='sum' '(' (expression_list=Expression_List | child=Children_ID) ')'	
	| op='mul' '(' (expression_list=Expression_List | child=Children_ID) ')'
	| op='min' '(' (expression_list=Expression_List | child=Children_ID) ')'
	| op='max' '(' (expression_list=Expression_List | child=Children_ID) ')'	
	| op='count' '(' (children='children' | children='selectedchildren') ')'	
	| op='avg' '(' (expression_list=Expression_List | child=Children_ID) ')'	
	| op='and' '(' (expression_list=Expression_List | child=Children_ID) ')'	
	| op='or' '(' (expression_list=Expression_List | child=Children_ID) ')'	
	| op='xor' '(' (expression_list=Expression_List | child=Children_ID) ')'
	| value='true'
	| value='false'
	| value=Integer
	| value=Real
	| ref=Long_ID;