 Truth in a model is then defined in terms of satisfaction. A variable assignment \(s\) for the model \(\langle D, I\rangle\) is a function from the set of variables of the language into the domain \(D\). A formula \(A\) is satisfied in a model \(\langle D, I\rangle\) by an assignment \(s\) of objects to variables. If \(s\) is a variable assignment for \(\langle D, I\rangle\), we write \(s[x/d]\) to specify a variable assignment, which is just like \(s\) except perhaps for assigning \(d\) in \(D\) to the variable \(x\).