This reference summarizes the properties and techniques of conceptual modeling and provides analyses of many examples of existing software. It examines the complexity and scale of software systems, including key components, relationships, user interfaces, and persistent data. The authors consider the impact of legacy systems, the inherently local nature of software systems, and the gap between formal software models and effective software development. They show how software models can be used to address increasingly complex systems that include data integrity, regression testing, security, scalability, portability, and usability.