This document discusses software modeling from a system perspective. It defines key concepts such as a system, system element, and block. A system is composed of interacting elements organized to achieve a purpose. A system element may itself be a system or an atomic entity. The document recommends using unified modeling concepts like "block" to represent a system, subsystem, component or other entity. It presents different modeling views including context, services, structure and behavior, and discusses modeling techniques like use case diagrams, activity diagrams and more.