Before revision: For a graph parameter \pi, the Contraction(\pi) problem consists in, given a graph G and two positive integers k,d, deciding whether one can contract at most k edges of G to obtain a graph in which \pi has dropped by at least d. Galby et al. [ISAAC 2019, MFCS 2019] recently studied the case where \pi is the size of a minimum dominating set.
After revision: For a graph invariant \pi, the Contraction(\pi) problem consists in, given a graph G and two positive integers k,d, deciding whether one can contract at most k edges of G to obtain a graph in which \pi has dropped by at least d. Galby et al. [ISAAC 2019, MFCS 2019] recently studied the case where \pi is the size of a minimum dominating set.