Enterprise AJAX has been written with intermediate-to-advanced server- side developers in mind (Java, object-oriented PHP, or ASP.NET). Many of the concepts in the book have been adopted from the time honored soft- ware engineering patterns introduced by the “gang of four” (that is, Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, authors of Design Patterns: Elements of Reusable Object-Oriented Software [Addison-Wesley Professional]). Readers would benefit from a basic understanding of software design patterns, or at least an interest in learn- ing more about them because they are applied throughout the book. We hope that delivering AJAX in a familiar way using patterns can help the more experienced developer understand the concepts and ideas more easily. Vlissides, authors of Design Patterns: Elements of Reusable Object-Oriented Software [Addison-Wesley Professional]). Readers would benefit from a basic understanding of software design patterns, or at least an interest in learn- ing more about them because they are applied throughout the book. We hope that delivering AJAX in a familiar way using patterns can help the more experienced developer understand the concepts and ideas more easily.