# Resilience in the Cyberworld: Definitions, Features and Models
## 2 Definitions  
In the literature of recent years, there have been many definitions of resilience, some of which differ considerably. As described in [3], the content of the definitions strongly depends on the respective fields of application. Resilience is derived from the Latin _resilire_, and can be translated as \"bouncing back\" or \"bouncing off\". In essence, the term is used to describe a particular form of resistance. How the term resilience is used in different other disciplines (material science, engineering, psychology, ecology) is described in [43]. Additionally, in computer science, the term resilience has been defined several times from different points of view. As described in [3] for example, resilience is often used as a synonym for fault tolerance. However, recent publications show that this approach has been replaced by the view that resilience is much more than fault tolerance (see [7]). In the following, we introduce the different definitions of resilience that we found in the literature, to provide a common understanding of resilience in general and for the \begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Year** & **Title and Author(s)** & **Further Sources** \\ \hline
**1** & 1976 & **A Principle for Resilient Sharing of Distributed Resources**[2] \\  & & _[PERSON]; [PERSON]_ \\
**2** & 2007 & **Release it! Design and Deploy Production-Ready Software**[11] & [12] \\  & & _[PERSON]_ \\
**3** & 2008 & **From Dependability to Resilience**[13] & [4; 14; 15] \\  & & _[PERSON]_ & [17; 18] \\
**4** & 2011 & **Prologue: The scope of resilience engineering**[16] & [17; 18] \\  & & _[PERSON]_ & [19; 20] \\  & & **On the Constituent Attributes of Software and Organisational Resilience** & \\
**5** & 2013 & [19] & [3; 20] \\  & & _[PERSON]_ & **Quantifying coastal system resilience for the US Army Corps of** \\
**6** & 2015 & **Engineeers**[6] & [21; 22; 23; 24] \\  & & _[PERSON]; [PERSON]; [PERSON]_ & [25] \\
**7** & 2016 & **What’s the Difference between Reliability and Resilience?**[25] & [26; 27] \\  & & _[PERSON]_ & **Systems Security Engineering: Cyber Resiliency Considerations for the** \\
**8** & **Engineering of Trustworthy Secure Systems (NIST Special Publication** & **800-160, Volume 2)**[7] & [28; 29; 30; 31; 32] \\  & & _[PERSON]; [PERSON]; [PERSON]; [PERSON]_ & **Systematic Approach to Cyber Resilience Operationalization in SMEs**[8] \\
**9** & 2020 & **[PERSON], [PERSON]. [PERSON], [PERSON],** & [33; 34; 35; 36] \\  & & _[PERSON], [PERSON]_ & \\
**10** & **2020** & **Foundations for Research in Cyber-Physical System Cyber Resilience** & \\
**10** & **2020** & **using State Estimation**[9] & [37; 38; 39; 40; 41; 42] \\  & & _[PERSON]. [PERSON], [PERSON], [PERSON]_ & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The columns “title”, “author(s)”, and “year” show the papers we used as the main sources for this work, the column “further sources” indicates additional publications that use the term resilience in a similar way to the main source in the same row. rest of this paper in particular. Definitions are taken, if available, from the publications in Table 1.  
One of the first definitions was presented 1976 in [2], and describes the concept of resilience as follows:  
_\"He (remark: the user) should be able to assume that the system will make a \"best-effort\" to continue service in the event that perfect service cannot be supported; and that the system will not fall apart when he does something he is not supposed to\"_. In addition, [2] mentions attributes that constitute resilience as part of its definition. The attributes are the following: **error detection, reliability, development capability** and **protection against misuse** in the sense that the misuse of a system by individual users has only negligible effects on other users. According to [PERSON] [2], these four attributes of a resilient system can be summarized as the attempt to describe extreme reliability and serviceability.