2. For each subsystem, the list of aspects relating to interoperability is indicated in the order given to the representative joint body for drawing up draft TSIs.
Under the provisions of Article 6(1), this order shall be established in accordance with the procedure laid down in Article 21(2).
Where necessary, the list of aspects relating to interoperability indicated in the order is specified by the representative joint body in accordance with the provisions of Article 5(3)(e).