 The first definitions of sequentiality, due to Vuillemin (1974) and Milner (1977) stated that an \(n\)-ary functions \(f\) over flat domains is sequential at argument \({\langle x_1,\ldots,x_n \rangle}\) if there is a sequentiality index \(i\) of \(f\), depending on \({\langle x_1,\ldots,x_n \rangle}\), such that every increase in the output information must increase the information at argument \(i\). For example, the function \(\texttt{cond} : {\mathbb{B}}_{\bot} \times {\mathbb{N}}_{\bot} \times {\mathbb{N}}_{\bot} \to {\mathbb{N}}_{\bot}\) is sequential in this sense at any input tuple. In fact, its sequentiality index at \({\langle \bot,m,n \rangle}\) is 1; its sequentiality index at \({\langle {\textit{tt}},m,n \rangle}\) is 2, and its sequentiality index at \({\langle {\textit{ff}},m,n \rangle}\) is 3. There is however no sequentiality index for the function \(\texttt{por} : {\mathbb{B}}_{\bot} \times {\mathbb{B}}_{\bot} \to {\mathbb{B}}_{\bot}\) at the input \({\langle \bot,\bot \rangle}\).