GROUP a
{
	INTEGER a1 DEFAULT 1
}
GROUP b IF a.a1 = 1
{
	INTEGER b1 DEFAULT 1
}
GROUP b IF a.a1 = 2
{
	INTEGER b2 DEFAULT 1
}

grammar org.xtext.example.config.MyConfig with org.eclipse.xtext.common.Terminals

generate myConfig "http://www.xtext.org/example/config/MyConfig"

Model:
	elements+=AbstractElements*;

AbstractElements:
	Parameter | Group;

Group:
	'GROUP' name=ID ('IF' (condition+=Condition)* )?
	'{'
		(parameters+=Parameter)*
	'}';

Parameter:
	'INTEGER'  name=ID 'DEFAULT' default=INT;

Condition:
	EquationCondition;

EquationCondition:
	group=[Group|ID]'.'parameter=[Parameter|ID] '=' value=INT;

composedCheck = "org.eclipse.xtext.validation.NamesAreUniqueValidator"