The general process in the discrete-time linear time-invariant (DLTI) direct feedthrough state-space model form is considered:
\begin{equation} \begin{cases} \boldsymbol{x}(k+1) = \boldsymbol{A} \boldsymbol{x}(k) + \boldsymbol{B} \boldsymbol{u}(k), \\ \boldsymbol{y}(k) = \boldsymbol{C} \boldsymbol{x}(k) + \boldsymbol{D} \boldsymbol{u}(k). \end{cases} \label{eq:DLTI} \end{equation}
For the DLTI system, the following set is defined such that $\boldsymbol{x}_k \in \mathcal{X}$, $\boldsymbol{y}_k \in \mathcal{Y}$, $k=0,1,\dots,N-1$:
\begin{equation} \mathcal{S} = \Bigg\{ \{ \boldsymbol{x}_0, \boldsymbol{u}_0,\boldsymbol{u}_1,\dots,\boldsymbol{u}_{N-1} \} :\ \mathbf{H} \boldsymbol{x}_0 + \mathbf{L}_0 \boldsymbol{u}_0 + \mathbf{L}_1 \boldsymbol{u}_1 + \dots + \mathbf{L}_{N-1} \boldsymbol{u}_{N-1} \leq \mathbf{K} \Bigg\}. \label{poly:safeSetapprox} \end{equation}
What is the official name for the set $\mathcal{S}$ that are used in the literature?