“…First, we give a brief overview to specify our strict framework, that is to say, the BPFs parameterization technique. Then, the challenging tasks investigated in this section will concern the extension of the direct approach (BPFs) to decentralized optimal control with observers of interconnected systems (Bichiou et al, 2018; Dadkhah and Farahi, 2015; Ghali et al, 2017a, b; Hosseinpour and Nazemi, 2016; Marzban, 2016; Tang et al, 2017; Warrad et al, 2018; Xie and Huang, 2016; Ziari et al, 2019).…”