of potential deceit. This list of challenges is illustrative rather than exhaustive, and it focuses on the challenges to the "unifying logic" and "proof" layers of the Semantic Web. The World Wide Web Consortium (W3C) Incubator Group for Uncertainty Reasoning for the World Wide Web (URW3-XG) final report lumps these problems together under the single heading of "uncertainty". Many of the techniques mentioned here will require extensions to the Web Ontology Language (OWL) for example to annotate conditional probabilities. This is an area of active research. Standards Standardization for Semantic Web in the context of Web 3.0 is under the care of W3C. Components The term "Semantic Web" is often used more specifically to refer to the formats and technologies that enable it. The collection, structuring and recovery of linked data are enabled by technologies that provide a formal description of concepts, terms, and relationships within a given knowledge domain. These technologies are specified as W3C standards and include: Resource Description Framework (RDF), a general method for describing information RDF Schema (RDFS) Simple Knowledge Organization System (SKOS) SPARQL, an RDF query language Notation3 (N3), designed with human readability in mind N-Triples, a format for storing and transmitting data Turtle (Terse RDF Triple Language) Web Ontology Language (OWL), a family of knowledge representation languages Rule Interchange Format (RIF), a framework of web rule language dialects supporting rule interchange on the Web JavaScript Object Notation for Linked Data (JSON-LD), a JSON-based method to describe data ActivityPub, a generic way for client and server to communicate with each other. This is used by the popular decentralized social network Mastodon. The Semantic Web Stack illustrates the architecture of the Semantic Web. The functions and relationships of the components can be summarized as follows: XML provides an elemental syntax for content structure within documents, yet associates no semantics with the meaning of the content contained within. XML is not at present a necessary component of Semantic Web technologies in most cases, as alternative syntaxes exist, such as Turtle. Turtle is a de facto standard, but has not been through a formal standardization process. XML Schema is a language for providing and restricting the structure and content of elements contained within XML documents. RDF is a simple language for expressing data models, which refer to objects ("web resources") and their relationships. An RDF-based model can be represented in a variety of syntaxes, e.g., RDF/XML, N3, Turtle,