Introduction: structure, syntax and semantics. The need for semantics on the Web. Meta-programming: Meta-data; XML schema; XSLT; RDF. Semantics: Semantics and knowledge; ontologies; logic; Concluding; Modeling ofdomains; Context. Distributed knowledge: Classification; Protocols based on knowledge. Technologies: Toolsfor working with ontologies; Software packages(API) for working with ontologies; OWL. Methodology: The methodology for ontology engineering; Methodologies for the introduction of knowledge management; Methodologies for the developmentof semantic systems. Semantic systems: Semantic web services, semantic web portals, Semantic Wiki, semantic multi-agent systems, semantic web browsers. Applications: bioinformatics, document management systems, information retrieval, and so on.