Let V be a finite set of n elements and F={X1,X2,>...,Xm} a family of m subsets of V. Two sets Xi and Xj of
F overlap if Xi∩Xj=∅,Xj∖Xi=∅, and Xi∖Xj=∅. Two sets X,Y∈F
are in the same overlap class if there is a series X=X1,X2,...,Xk=Y of
sets of F in which each XiXi+1 overlaps. In this note, we focus
on efficiently identifying all overlap classes in O(n+∑i=1m∣Xi∣)
time. We thus revisit the clever algorithm of Dahlhaus of which we give a clear
presentation and that we simplify to make it practical and implementable in its
real worst case complexity. An useful variant of Dahlhaus's approach is also
explained