How to force a generic type parameter to be an interface?

Is there a way in java to specify, that the type parameter of a generic class must be an interface (not just extending it!)

What I want to do is the following:

public class MyClass<X extends SomeInterface, Y extends SomeOtherClass & X>

Meaning that Y must be a subclass of SomeOtherClass AND implement X. What I currently get by the compiler is

The type X is not an interface; it cannot be specified as a bounded parameter

So, how can I tell the compiler that X must always be an interface?

Edit:
OK, I guess I oversimplified my problem a bit. Let's use my actual application domain to make it more clear:

I have an API for representing diagrams. A Diagram contains Node and Edge objects. All these three classes implement the Shape interface. Shapes may have child shapes, a parent shape and belong to a diagram.

The thing is, that I need to make two versions of this API: one open-source with just basic functionality and an extended one with more features. However, the extended API must only provide methods, which return the extended types (ExtendedDiagram, ExtendedNode, ExtendedEdge and (here comes the problem) ExtendedShape).
So I have something like this:

/* BASIC CLASSES */
public interface Shape<X extends Shape<X,Y>, Y extends Diagram<X,Y>>{
    public List<X> getChildShapes();
    public X getParent();
    public Y getDiagram();
    ...
}

public class Diagram<X extends Shape<X,Y>, Y extends Diagram<X,Y>> implements Shape<X,Y>{...}
public class Edge<X extends Shape<X,Y>, Y extends Diagram<X,Y>> implements Shape<X,Y>{...}
...

/* EXTENDED CLASSES */
public interface ExtendedShape extends Shape<ExtendedS