From d4c3a916398e4eee9c1eaaa840968d4b19f40c91 Mon Sep 17 00:00:00 2001
From: mjkwiatkowski <mati.rewa@gmail.com>
Date: Wed, 15 Jul 2026 15:56:09 +0200
Subject: feat: finished section 2.4.3

---
 content/background.tex | 55 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

(limited to 'content/background.tex')

diff --git a/content/background.tex b/content/background.tex
index 17d7d47..6e39e6d 100644
--- a/content/background.tex
+++ b/content/background.tex
@@ -158,7 +158,7 @@ We select only the digital twins that adhere closest to the \gls{nasem} definiti
 The aim of this survey is to search and organize the field of \gls{dcdt}s.
 In this subsection, we describe the methods for collecting relevant scientific articles and present the design of the system model for generic \gls{dcdt}s.
 
-\begin{enumerate}[label=\textbf{\arabic*.}, align=left]
+\begin{enumerate}[label=\textbf{\arabic*.}]
 	\item \textbf{Review Strategy}\\
 	      The most common methods for conducting literature surveys are \begin{enumerate*}[label=(\arabic*)]
 		      \item random traversal of the related literature,
@@ -262,6 +262,59 @@ Kalibre takes the best of both \gls{ml} and \gls{cfd} approaches and achieves su
 
 \subsection{System Model for Datacenter Digital Twinning}
 \label{ss:system_model_for_dcdts}
+In \Cref{fig:system_model} we present a holistic model of \gls{dcdt}s from \Cref{sss:advanced_dts}.
+The figure includes the functionality present in the majority of \gls{dcdt}s, combined together into a unified model.
+We distinguish 3 core elements of every \gls{dcdt}:
+\begin{enumerate*}[label=(\arabic*)]
+	\item the virtual world
+	\item digital thread
+	\item the physical world
+\end{enumerate*}.
+\begin{enumerate}[label=\textbf{\arabic*.}]
+	\item \textbf{Virtual World} contains the \gls{dcdt}.
+	      It represents all the components that exist in software.
+	      Every \gls{dcdt} model can be categorized into two sub-categories:
+	      \begin{enumerate*}[label=(\arabic*)]
+		      \item infrastructure model
+		      \item operations model
+	      \end{enumerate*}.
+	      Each \gls{dcdt} from \Cref{sss:advanced_dts} contains a model of the infrastructure within the datacenter.
+	      This includes virtual replicas of the hardware elements (\eg servers, networking, server racks, rooms).
+	      These elements have varying degrees of fidelity.
+	      For example, NetGraph models the datacenter interconnect using purely configuration files.
+	      On the contrary ExaDigiT models the datacenter hardware fully in 3D.
+	      Both offer virtual infrastructure models as a part of the \gls{dcdt}.
+
+	      The operations model is likewise present in all deployments.
+	      It models the \emph{behaviour} of the datacenter, \ie the data flow, the different workloads running on the compute, the amount of data stored in each hosts \etc.
+	      Both the infrastructure model and the operations model are part of all \gls{dcdt} deployments from \Cref{sss:advanced_dts}.
+	      A digital twin that contains only the infrastructure model, cannot enable insights into the real-time operation of the datacenter.
+	      Likewise, a \gls{dcdt} containing just the operations model does not possess a capability to \eg simulate the datacenter.
+	      Only both, combined together enable the insights envisioned by the \gls{nasem} \gls{dt} definition~\cite{DBLP:usdoe/report/AP26894}.
+	\item \textbf{Digital Thread} connects the virtual world to the physical world.
+	      This is a novel contribution of our thesis.
+	      The digital thread is a \emph{conceptual} element that unites the components which do not belong in either of the worlds.
+	      All \gls{dcdt} programs from \Cref{sss:advanced_dts} contain elements that are ``in-between'' the physical and virtual twin.
+	      After comparing and corroborating these components across deployments, we find 4 that prevail the most:
+	      \begin{enumerate*}[label=(\arabic*)]
+		      \item the visualization interface
+		      \item the message broker
+		      \item the monitoring system
+		      \item the system knobs
+	      \end{enumerate*}.
+	      These elements \emph{connect} facilitate the connection between the physical and the virtual.
+	      For example, the visualization interface provides insights from the metrics collected by the \gls{dcdt} (virtual world) to the datacenter operators (physical world).
+	      The message broker transfers the data from the real datacenter (physical world) to the digital twin (virtual world).
+	\item \textbf{Physical World} models the real datacenter.
+	      All deployments in \Cref{sss:advanced_dts} contain this element.
+	      Moreover, within the datacenter, we distinguish between 3 core elements that are necessary to model the datacenter faithfully\begin{enumerate*}[label=(\arabic*)]
+		      \item the \gls{it} equipment
+		      \item cooling subsystem
+		      \item power supply
+	      \end{enumerate*}.
+	      All of the aforementioned systems from \Cref{sss:advanced_dts} model either of the 3 elements.
+	      In order to adhere to the holistic view of \gls{dcdt}s, and to fulfill the \gls{nasem}'s definition, the system must contain all 3 of these elements.
+\end{enumerate}
 
 \begin{figure}[t]
 	\centering
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