Because the only requirement to start a production statement is that the caller is able to create a Producer (which can be any type of Object in the java sense), any object can start a production. Within rules, after the query the query graph is responsible for creating the producer. In the case of RGG, it creates a RGGProducer.

Within normal statement blocks (in a java block), any Object can serve to create the “Producer”, there are not interface or class to extend. It only need to implements the required methods, which are retrieved at compile time.

class AnyClass {
 
	public AnyClass producer$begin() {
		// do smthg
		return this;
	}
	public AnyClass producer$end() {
		// do smthg
		return this;
	}
	public AnyClass operator$space(Node node) {
		// do smthg
		return this;
	}
	public AnyClass custoMethod(Node node) {
		// do smthg
		return this;
	}
}
 
public void java_method(){
	AnyClass t = new AnyClass();
	t ==> Node Node -custoMethod-> Node ;
}