This chapter introduces the object-oriented paradigm and the UML's modeling techniques. As the UML is a language for communicating about a system and its requirements, we communicate our understanding of the subject using an alphabet, words, sentences, paragraphs, sections, and documents. First, I discuss how to write sentencesUML diagram fragmentsabout the subject using the language's alphabet and words, and I also introduce the concepts and principles of the object-oriented paradigm. Next, I talk about how sentences are organized into paragraphsUML diagramsand I introduce the various UML modeling techniques. Next, I go over how paragraphs are organized into sectionsarchitectural views. Finally, I discuss how sections are organized into documentsmodels. Many details are not fleshed out in this chapter but are more fully elaborated in subsequent chapters.