F20 Performance Work is declared as a subclass of F16 Container Work. This implies that the incorporated expressions (such as the text of the staged play, the text of the argument for the ballet, the recorded music to be used for the ballet, or the content of the musical score to be used for a concert, etc.) are not by themselves a part of the expression of this F1 Work. Rather, an expression (F25 Performance Plan) of the instructions the stage production, choreography or musical performance consists of incorporates (R14) that textual or musical content. In other words, the text of "Hamlet" is not a component of the concepts that underlie a given mise-en-scène of "Hamlet", but any staging directions (F25 Performance Plan) that convey a given director's vision of "Hamlet" must necessarily incorporate the text of "Hamlet".