The monograph explores the problem of knowledge representation and processing in intelligent systems. Based on a comprehensive analysis of known models of knowledge representation and methods of knowledge processing, it was shown that the solution to the problem under study should be based on the application of mathematical modeling methodology. Based on this, an analysis of the natural properties of declarative and procedural knowledge was carried out, on the basis of which the properties of a new model of knowledge representation - a logical-computational semantic network (LAN-network) are substantiated. The properties of the LAN network have been formally investigated, and it has been shown that the LAN network surpasses a number of other known network models of knowledge representation in its functionality. A set of knowledge processing methods has been proposed for the LAN network, including: a direct inference method, a method for constructing the initial state of the direct inference process, static verification methods and a method for generating many test cases. Based on the obtained theoretical results, a software-tool knowledge presentation and processing environment (SLM-technology) has been developed, which is, on the one hand, a tool for building knowledge-based systems, on the other hand, an integrated modeling environment. Substantial examples of the use of SLM technology for presenting and processing knowledge about various subject areas are given. For researchers and specialists engaged in research and development in both the field of intelligent systems and mathematical modeling, as well as graduate students and students of relevant specialties.