From 003b5a4727f668725300558267d3023136f75bd2 Mon Sep 17 00:00:00 2001
From: Alexandru Iosup <alexandru.iosup@gmail.com>
Date: Mon, 27 Jul 2026 10:37:58 +0000
Subject: Update on Overleaf.

---
 content/background.tex | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

(limited to 'content/background.tex')

diff --git a/content/background.tex b/content/background.tex
index 68ce6a2..74083e5 100644
--- a/content/background.tex
+++ b/content/background.tex
@@ -1,12 +1,12 @@
 \chapter{Background}\label{s:background}
 \section{Overview}\label{ss:background_overview}
 \begin{mynote}
-	The contribution in this chapter is three-fold:
+	Addressing RQ$_1$, the contribution in this chapter is three-fold:
 
 	\begin{enumerate}[label=\emph{C\textsubscript{\arabic*}}, itemsep=0.2pt]
-		\item We provide a brief overview on datacenters (\Cref{ss:datacenters}) datacenter simulation (\Cref{sss:simulation}), compute failures (\Cref{sss:failures}), and digital twinning (\Cref{ss:digital-twinning}).
-		\item We survey the state-of-the-art concerning datacenter digital twinning (\Cref{sss:advanced_dts}).
-		\item We construct a system model for existing datacenter digital twins (\Cref{ss:system_model_for_dcdts})
+		\item We provide a brief overview on datacenters (\Cref{ss:datacenters}) datacenter simulation (\Cref{sss:simulation}), compute failures (\Cref{sss:failures}), and digital twinning~ (\Cref{ss:digital-twinning}).
+		\item We survey the state-of-the-art concerning datacenter digital twinning~ (\Cref{sss:advanced_dts}).
+		\item We propose a system model (architecture) for datacenter digital twins, including a novel Digital Thread component for the operational needs linking the digital with the physical worlds~(\Cref{ss:system_model_for_dcdts}).
 	\end{enumerate}
 \end{mynote}
 
@@ -28,7 +28,7 @@ An example datacenter in \gls{cern}, is depicted on \Cref{fig:datacenter}.
 \begin{figure}[t]
 	\centering
 	\includegraphics[width=0.9\linewidth]{images/datacenter.jpg}
-	\caption[Datacenter in CERN.]{Example of a datacenter in \gls{cern}, Switzerland (2010)~\cite{Wikipedia:article/Datacenter}. In the figure we can see servers within servers racks, and the network cables.}
+	\caption[Datacenter in CERN.]{Example of a datacenter in \gls{cern}, Switzerland (2010)~\cite{Wikipedia:article/Datacenter}. The figure depicts servers within servers racks, and network cables interconnecting them.}
 	\label{fig:datacenter}
 \end{figure}
 
@@ -120,11 +120,11 @@ The longer the \gls{dt} is working, the more accurate its predictions, because a
 A generic \gls{dt} architecture is depicted in Figure \ref{fig:five_dimensional_dt} from Tao \etal~\cite{DBLP:conf/cirp/TAO2018169}.
 
 % Why has not anyone done this before?
-Digital twinning has only recently become feasible because of the developments in \gls{hpc}.
-Between 2003 and 2011 the compute needed to run a \gls{dt} was simply not present.
+Although digital twinning through simplified models exists since the 1960s, detailed and accurate digital twinning of complex and realistic scenarios has only recently become feasible because of developments in \gls{hpc}.
+Between 2003 and 2011, the compute needed to run a \gls{dt} was simply not present or was (largely) unaffordable.
 As such, while the concept existed, the hardware did not catch up yet.
 However, in the last decade, multicore computing paradigms and the advent of GPU computing has finally enabled computation needed to run digital twins.
-As a result, digital twins have become more relevant today than 10 years ago~\cite{DBLP:conf/cirp/TAO2018169}.
+As a result, digital twins have become more relevant today than a decade ago~\cite{DBLP:conf/cirp/TAO2018169}.
 
 A crucial part any of any \gls{dt} is \emph{predictive modelling}, which drives actionable insights~\cite{DBLP:usdoe/report/AP26894} (see \Cref{fig:predictive_analytics}).
 \begin{figure}[t]
@@ -270,7 +270,7 @@ Kalibre takes the best of both \gls{ml} and \gls{cfd} approaches and achieves su
 \end{figure}
 \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}.
+In \Cref{fig:system_model} we propose a new, 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*)]
@@ -299,7 +299,7 @@ We distinguish 3 core elements of every \gls{dcdt}:
 	      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.
+	\item \textbf{(novel) 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.
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