JAVA DATA OBJECfS (JDO) specifies a transparent persistence service for Java objects. The specification describes a general framework for storing and retrieving the per­ sistent state ofJava objects. The JSR-12 expert group defined JDO using the Java Community Process. JDO includes a specification, a reference implementation, and a technology compatibility kit (TCK). All three can be downloaded from the JavaCommunityProcessWebsite (http://W~M.jcp.org/jsr/detail/12.jsp). Anumber of vendors have created implementations of JDO and provide versions of their products that you can download from the Web. URLs to some of these vendors are found near the end of this introduction. Java programmers use tools to make their projects successful. Most applications and server-side components involve moving data between objects in memory and persistent storage. JDO promises to change the way that Java programmers store and retrieve object state. JDO simplifies the application's code, increases the appli­ cation's portability, and helps to separate concerns in the application's design. Compared to existing alternatives, JDO makes persistence easier to understand, easier to model, and easier to code. Who Should Read This Book This book is intended for Java programmers and application architects. It assumes that you know how to program in Java, and it assumes that you want to use JDO and understand how it works. This book emphasizes what you need to know to use JDO effectively.