Algorithm 1 SDM

Input:Stream X, distance metric $d(·,·)$, parameter $\epsilon \in (0,1)$, solution size $k\in {\mathbb{Z}}^{+}$ Output: A set $S\subseteq X$ with $\left|S\right|=k$ 1:$\mathcal{U}=\{\frac{d_{min}}{{(1-\epsilon )}^j}:j\in {\mathbb{Z}}_0^{+}\wedge {(1-\epsilon )}^j\ge \frac{d_{min}}{d_{max}}\}$ 2:Initialize $S_{\mu }=\varnothing$ for each $\mu \in \mathcal{U}$ 3:for all $x\in X$ do 4:    for all $\mu \in \mathcal{U}$ do 5:        if $\left|S_{\mu }\right|<k$ and $d(x,S_{\mu })\ge \mu$ then 6:           $S_{\mu }\leftarrow S_{\mu }\cup \left\{x\right\}$ 7:return $S\leftarrow {arg\; max}_{\mu \in \mathcal{U}:\left|S_{\mu }\right|=k}div\left(S_{\mu }\right)$