This IBM Redbook describes the new concept of Web services from various perspectives. It presents the major building blocks Web services rely on. Here, well-defined standards and new concepts are presented and discussed. Whereas these concepts are described vendor-independent, the book also presents IBM's view and illustrates with suitable demonstration applications how Web services can be implemented using IBM's product portfolio, especially WebSphere Application Server Version 5 and WebSphere Studio Application Developer Version 5. This book is a major update to the IBM Redbook Web Services Wizardry with WebSphere Studio Application Developer, SG24-6292, published in 2002. This book is structured in two parts: Part 1 presents the underlying concepts for the use of Web services. It presents the basic programming model, well-known basics in an updated way, and new concepts that go beyond the scope of the 2002 book. Part 2 shows how Web services can be implemented using the latest IBM tools. Here, we introduce a sample application that is demonstrated in various different ways.