A selection engine for a cooperative processing network, in which databases compute portions of searches and analyses which they may most efficiently compute. formed by a process comprising the step of contacting: from 1 to 2 equivalents of a compound of formula AlX3 wherein each X independently represents Cl, Br or F; with 1 equivalent of a compound of formula R1\u2014C\u2014N wherein R1 to R3 have meanings given in the description. A communicating member is attached to each latch clasp with a communicating member pivot.