 An assignment for a model \(M = (W, R, V)\) is a function \(g\) that assigns an element of \(W\) to each nominal. An assignment \(g'\) is an \(\mathtt{a}\)-variant of \(g\) if \(g'\) agrees with \(g\) on all nominals save possibly \(\mathtt{a}\). The relation \(M, g, w \vDash \phi\) is defined by induction, where \(g\) is an assignment, \(w\) is an element of \(W\), and \(\mathtt{\phi}\) is a formula.