Definition of Model of an Algebraic Curve I'm reading the classical paper of Arakelov "Intersection Theory of Divisors on an Arithmetic Surface". At the very beginning he uses the notion of model of a curve.
In specific we have a number field $K$ with ring of integers $R$, $X$ is a smooth complete algebraic curve over $K$. Here Arakelov writes: "Let $V$ be any smooth and complete model of $X$ over $R$."
What does it mean? I didn't find the definition nor googling it, neither looking on the books "Algebraic Geometry" of Hartshorne and "Introduction to Intersection Theory in Algebraic Geometry" of Fulton.
 A: The real answer has been given by KCd in the comments to the question. I answer my own question to have an explicit answer written under the question and to mark the question as answered (because in fact it is).
According to Definition $1.1$ of Liu´s Algebraic Geometry and Arithmetic Curves, Chapter 10 paragraph 10.1.1:
Let $S$ be a Dedekind scheme of dimension $1$, with function field $K$. Let $C$ be a normal, connected, projective curve over $K$. We call a normal fibered surface $\mathcal{C} \rightarrow S$ together with an isomorphism $f:\mathcal{C}_\eta \simeq C$ a model of $C$ over $S$. We will say that and a regular model of $C$ if $\mathcal{C}$ is regular. More generally, we will say that a model $(\mathcal{C},f)$ verifies a property $(P)$ if $\mathcal{C} \rightarrow S$ verifies $(P)$. The property $(P)$ can, for example, be the fact of being smooth, minimal regular, or regular with normal crossings, etc. A morphism $\mathcal{C} \rightarrow \mathcal{C}^´$ of two models of $C$ is a morphism of $S$-schemes that is compatible with the isomorphisms $\mathcal{C}_\eta \simeq C$, $\mathcal{C}^´_\eta \simeq C$.
