Within each subspace a full-CI expansion is generated (complete set of intra-space excitations), while the number of inter-space excitations is restricted. 18,24,27,28 GAS spaces are defined disconnected if no inter-space excitations are permitted, while they are defined connected if inter-space excitations are allowed. In the same GAS wave function both connected and disconnected spaces can exist. Figure depicts a possible specification of GAS constraints.