# A Comprehensive Survey on Knowledge-Defined Networking
## 3 Knowledge Plane  
### Introduction to Knowledge Plane  
The knowledge plane is a logical layer that is responsible for generating, processing, and disseminating knowledge about the network. The knowledge plane helps network operators improve their ability to manage network behavior and adapt to changing conditions. The knowledge plane includes various types of knowledge, such as declarative knowledge (rules), procedural knowledge (processes), and contextual knowledge (knowledge about the environment and the conditions in which the network operates) [63]. The data for generating knowledge can come from various sources, such as network devices, sensors, etc., which are analyzed to generate insights and enable intelligent decision-making. By making full use of the knowledge plane, network operators can proactively identify and address issues before they become problems, optimize network behavior to meet changing demands, and implement advanced security measures to protect against threats.  
Knowledge representation/modeling languages can be used to represent and manipulate knowledge in a machine-readable format. They provide the data model and syntax for representing the knowledge. Resource Description Framework (RDF), Web Ontology Language (OWL), Ontology Inference Layer (OIL), RDF Schema (RDFS), and Knowledge Interchange Format (KIF) are the main knowledge representation languages that have been proposed to be utilized in knowledge-defined networks. These knowledge representations are discussed in detail in subsequent sections.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Parameter/Feature** & **Traditional Network** & **SDN** & **KDN** \\ \hline Logical planes & Data, control, and application coupled & Data, control, and application decoupled & Data, control, management, knowledge, and application decoupled \\ \hline Network programmability & Manual and complex & Manual and simple & Hybrid and simple \\ \hline Control plane & Distributed across devices & Logically centralized and driven by application policies & Logically centralized and self learning driven by application policies and knowledge \\ \hline Management plane & Manual and distributed & Manual and centralized coupled with control plane & Hybrid and centralized decoupled from control plane \\ \hline Knowledge plane & Totally knowledge ignorant & Knowledge ignorant. However, make use of global network information in arriving at decisions & Generate knowledge, compose knowledge, generate rules, store and disseminate them to other planes \\ \hline Application plane & Tightly coupled with infrastructure infrastructure and inflexible & Decoupled with infrastructure needefined dynamically based on service needs & Decoupled from infrastructure, can be redefined and optimized based on service needs and network performance \\ \hline Network architecture & Static & Flexible & Flexible, self learning, and automated \\ \hline Operational cost & High & Medium & Low \\ \hline Implementation cost & Low & Medium & High \\ \hline Security features & Low & Medium & High \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of KDN, SDN, and traditional networks.