(1) Within the time-limit agreed by the parties or set by the arbitral tribunal, the claimant is to state the claim and the facts supporting the claim, and the respondent is to state their defence in their regard. In this context, the parties may submit all documents they consider to be relevant, or they may designate any other evidence of which they intend to avail themselves.
(2) Unless otherwise agreed by the parties, each of them may amend or supplement their claim or the means of attack or defence in the course of the arbitral proceedings; this does not apply if the arbitral tribunal does not allow such amendments or supplementations to be made because they were filed late without sufficient cause excusing the delay having been submitted
(3) Subsections (1) and (2) apply accordingly to any countersuits that may be brought.