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Could you please tell me why $\mathcal{V}$ is upward-direct? I know that for any $V,W\in \mathcal{V}$ there's $Z\in\mathcal{V}$ such that $(V\cup W)\cap S\subseteq Z\cap S$. But I can't find $Z\in\mathcal{V}$ such that $V\cup W\subseteq Z$.