This free e-book focuses on the SOA approach to integration of existing (legacy) applications and newly developed solutions, using modern technologies, particularly web services, XML, ESB, and BPEL. The book shows how to define SOA for integration, what integration patterns to use, which technologies to use, and how to best integrate existing applications with modern e-business solutions. It also shows how to develop web services and BPEL processes, and how to process and manage XML documents from the JEE and .NET platforms. Finally, it also explains how to integrate both platforms using web services and ESBs.