Lemma 32.19.1. Let $S$ be a scheme. Let $s \in S$ be a closed point such that $U = S \setminus \{ s\} \to S$ is quasi-compact. With $V = \mathop{\mathrm{Spec}}(\mathcal{O}_{S, s}) \setminus \{ s\} $ the base change functor

\[ \left\{ \begin{matrix} f : X \to S\text{ of finite presentation}
\\ f^{-1}(U) \to U\text{ is an isomorphism}
\end{matrix} \right\} \longrightarrow \left\{ \begin{matrix} g : Y \to \mathop{\mathrm{Spec}}(\mathcal{O}_{S, s})\text{ of finite presentation}
\\ g^{-1}(V) \to V\text{ is an isomorphism}
\end{matrix} \right\} \]

is an equivalence of categories.

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