In German law, there is the possibility of letting a third party determine the performance. If the parties decide to do this and make the contractual agreement for all those involved to have individual contentious questions clarified in a binding form by an independent and neutral third party, reference is made to an expert report for arbitration (out-of-court proceedings). This must not be mixed up with arbitration proceedings.
In principle, it is applicable to the parties that, if a corresponding agreement was made, the performance determined by the expert report is binding on the parties.
The advantage of this arrangement relates to the fact that the parties stipulate jointly and by mutual consent, for example, that a GSI employee should be active as an arbitration expert, what his/her tasks and obligations are, what questions are to be clarified etc.