Cationic starch graft copolymer composed of the monomers a) to d) a) 20-80% by weight of acrylamide, methacrylamide or mixtures thereof, b) 3-20% by weight of at least one basic or cationic vinyl monomer, c) 0. The format of the hierarchical data structure may be XML. The joint mechanism further includes a valve arrangement controlling the flow of hydraulic fluid between the chambers.