Vala implementing interfaces

/* Errors:
model.vala:21.3-21.18: warning: Movable.Position.Move hides inherited method `Movable.Movable.Move'. Use the `new' keyword if hiding was intentional
        public void Move (int x, int y) {
        ^^^^^^^^^^^^^^^^
model.vala:26.3-26.14: warning: Movable.Position.X hides inherited method `Movable.Movable.X'. Use the `new' keyword if hiding was intentional
        public int X() { return x; }
        ^^^^^^^^^^^^
model.vala:27.3-27.14: warning: Movable.Position.Y hides inherited method `Movable.Movable.Y'. Use the `new' keyword if hiding was intentional
        public int Y() { return y; }
        ^^^^^^^^^^^^
model.vala:12.2-12.25: error: `Movable.Position' does not implement abstract method `Movable.Movable.Move'
    class Position : Movable {
    ^^^^^^^^^^^^^^^^^^^^^^^^
model.vala:12.2-12.25: error: `Movable.Position' does not implement abstract method `Movable.Movable.X'
    class Position : Movable {
    ^^^^^^^^^^^^^^^^^^^^^^^^
model.vala:12.2-12.25: error: `Movable.Position' does not implement abstract method `Movable.Movable.Y'
    class Position : Movable {
    ^^^^^^^^^^^^^^^^^^^^^^^^
Compilation failed: 3 error(s), 3 warning(s)
*/

namespace Movable {
    abstract class Movable {
        public abstract void Move (int x, int y);
        public abstract int X();
        public abstract int Y();
    }

    class Position : Movable {
        int x;
        int y;

        public Position (int x, int y) {
            this.x = x;
            this.y = y;
        }

        public void Move (int x, int y) {
            this.x = x;
            this.y = y;
        }

        public int X() { return x; }
        public int Y() { return y; }
    }
}