Knowledge representation is the science, technology, and application of methods and tools to represent knowledge in such a way that it can be optimally searched for and found in digital databases. It enables the design of information architectures that, based on terms and conceptual orders, allow knowledge to be represented in its context of meaning. Without elaborate techniques of knowledge representation, it is impossible to design the semantic web. The textbook provides knowledge about metadata and describes in detail both documentary and library approaches to indexing content, such as thesauri and classification systems, efforts of computer science to create conceptual orders (ontologies), and user-centered developments in Web 2.0 (folksonomies). It focuses on the evaluation and provision of information.