Logical Approach to Systems Theory (LAST) provides the foundations for the second order treatment of system models and an effective framework for applying basic concepts in systems theory to the design of information systems. The main characteristics of LAST are: 1. type-free representation of system models; 2. distinction of system models from their structures; 3. hierarchical structure expansion, which describes inheritance of structures. The basic concept of LAST mainly focuses on a system model structure, morphism for similarity and universality of realization. This book provides a comprehensive treatment of the basic concepts and additional discussion of such important issues as hierarchy and system properties.