Kowledge bases: Languages, Ontologies, Knowledge Graphs, SPARQL and others associated elements in the context of Internet Infrastructure

The Internet's complex infrastructure generates an exponential volume of information that is often disconnected and difficult to comprehend. To address this, organizing, representing, and utilizing the knowledge within this infrastructure is crucial. This scenario highlights the fundamental role of formal languages, ontologies, knowledge graphs (KGs), and query languages like SPARQL. The construction of systems that can comprehend and manipulate knowledge is not trivial, involving the challenge of formalizing reasoning, which is linked to computability foundations. Concepts from mathematicians such as Kurt Gödel, Alan Turing, and Alonzo Church established the limits of what is computable and decidable. In knowledge representation, expressivity—how well a language captures real-world nuances—often conflicts with decidability—the guarantee that all inferences and queries can be resolved in finite time. Chomsky's hierarchy illustrates how language capabilities and complexities impact the expressive power of ontology and graph languages, making this balance a continuous concern. This article explores how theoretical and practical elements transform raw Internet infrastructure data into actionable knowledge. It discusses the crucial role of Semantic Web languages like RDF and OWL in formalizing and standardizing information representation, considering their expressivity and decidability. The text delves into ontologies, which provide the vocabulary and conceptual structure for modeling infrastructure components and relationships. KGs are presented as central databases that instantiate these ontologies with real-world facts, offering a unified and semantically rich network view. Finally, SPARQL is addressed as the standard language for querying these knowledge bases, enabling analysis, management, and automation. The article concludes by presenting tools and methodologies for building and exploring these bases, emphasizing their importance for the resilience, efficiency, and intelligence of 21st-century Internet infrastructure, while acknowledging the limits and possibilities imposed by computing foundations.