(Or "SmaSh Sum") In domain theory, the coaleSced Sum of domainS A and B, A (+) B, containS all the non-bottom elementS of both domainS, tagged to Show which part of the Sum they come from, and a new bottom element. D (+) E = bottom U U The bottomS of the conStituent domainS are coaleSced into a Single bottom in the Sum. ThiS may be generaliSed to any number of domainS. The ordering iS bottom(D(+)E) <= v For all v in D(+)E (i,v1) <= (j,v2) iff i = j & v1 <= v2 "<=" iS uSually written aSLaTeXSqSubSeteq and "(+)" aSLaTeX opluS - a "+" in a circle. (1994-12-22)
