This document provides an introduction to object-oriented analysis (OOA) and the Unified Modeling Language (UML). It discusses why modeling software systems is important and introduces UML as a standard modeling language. The core components of UML include diagrams like use case diagrams, which visually depict interactions between external users and a system. Use case diagrams show actors, use cases, and relationships between them like generalization, inclusion, and extension. The document uses examples and exercises to demonstrate how to construct use case diagrams for modeling different systems and scenarios.