Integral domains in which each ideal is a w-ideal

In this paper, we investigate integral domains in which each ideal is a w-ideal (i.e. the d- and w-operations are the same), called the D W-domains. In some sense this study is similar to that one given in Houston and Zafrullah (1988) [Houston, E., Zafrullah, M. (1988). Integral domains in which each t-ideal is divisorial. Michigan Math. J. 35:291-300.] for the T V-domains. We prove that a domain R is a D W-domain if and only if each maximal ideal of R is a w-ideal, and if R is a domain such that R_M is a D W-ideal for each maximal ideal M of R, then so is R, and the equivalence holds when R is v-coherent. We describe the w-operation on pull-backs in order to provide original examples.