Nowadays, newly developed software packages are often obsolete already at the time of their introduction. Object-oriented software development is a possible—if not the only—solution to this dilemma: applications are modeled as software objects that describe the properties and the behavior of real-world entities. Such objects are encapsulated, in that they hide—behind a publicly known interface—the complexity of their internal data structures and behaviors. This enables objects to be used in a wide range of program packages without needing to know the details of their internal implementation. Linking object-oriented modeled applications with a database places special demands on a database management system and development environment when the usual performance and semantics losses are to be avoided. This book provides a detailed description of the object model of the Caché postrelational database. This second, revised and expanded edition includes the many new features of Caché 5. There is a comprehensive description of the new Caché Studio with its improvements for developing and debugging applications as well as a whole new chapter about XML and SOAP based Web Services. The chapters about Java, ActiveX and the SQL manager have undergone a complete revision.