...
AnotherObject:
    'AnotherObject' attr=INT
    ;

Another:
'Object' name = ID '{'
    (
         ('Attribute1' ':' attribute1= INT)?
       & ('Attribute2' ':' attribute2= INT)?
       & ('Attribute3' (attribute3 += Object)(',' attribute3+= Object)*)?
    )
'}'
...

Object MyObject {
    Attribute1: 1
    Attribute3 AnotherObject 1
}

Object MyObject {
    Attribute1: 1
    Attribute3 AnotherObject 1Attribute3 AnotherObject 2}

Object MyObject {
    Attribute1: 1
    Attribute3 AnotherObject 1, AnotherObject 2
}

class MyDslRuntimeModule extends AbstractMyDslRuntimeModule {
	
	def Class<? extends PdaUtil> bindPdaUtil() {
		return MyDslPDAUtil
	}
}

public class MyDslPDAUtil extends PdaUtil {
	
	@Override
	public <S, P, E, T, D extends Pda<S, P>> D create(Cfg<E, T> cfg, FollowerFunction<E> ff,
			PdaFactory<D, S, P, ? super E> fact) {
		((FollowerFunctionImpl<E, T>)ff).setUnorderedStrategy(UnorderedStrategy.SEQUENCE);
		return super.create(cfg, ff, fact);
	}

}