The parties, witnesses and experts to be heard must be invited to appear to give evidence on the date fixed. The summons must be notified. At least two months' notice of a summons issued to a party, witness or expert to give evidence must be given, unless they agree to a shorter period. The summons must contain:[Art. 119; Rule 118(1); Rule 118(2); ]

(i)an extract from the order to take evidence, indicating in particular the date, time and place of the investigation ordered, whether it will be conducted by videoconference and stating the facts regarding which parties, witnesses and experts are to be heard;[Rule 118(2)(a); ]

(ii)the names of the parties to the proceedings and particulars of the rights which the witnesses or experts may invoke (see E‑IV, 1.10); [Rule 118(2)(b); ]

(iii)an indication that a party, witness or expert who has been summoned to appear before the European Patent Office on its premises may, at their request, be heard by videoconference; and[Rule 118(2)(c); ]

(iv)an indication that any party, witness or expert may request to be heard by the competent court of their country of residence and a requirement that they inform the EPO within a time limit to be fixed by the EPO whether they are prepared to appear before it (see E‑IV, 3.2.2 (iii) and E‑IV, 3.2.2 (iv)).[Rule 118(2)(d); ]

Even if evidence is not taken in oral proceedings, all parties to the proceedings may attend an investigation. Parties not summoned are informed thereof within the period laid down in Rule 118(2), together with a statement that they may attend.[Rule 119(3); ]