At the heart of Web services today are SOAP and WSDL, so it's important that you have a good understanding of them and how they're used. That said, memorizing the details of SOAP and WSDL is not critical. While these technologies are central to Web services, in many cases you may not deal with them directly, as they will be hidden in the communication and deployment layer of the J2EE Web Services platform.

This part of the book covers SOAP 1.1 and WSDL 1.1. Although support for SOAP 1.1 and WSDL 1.1 is required by the WS-I Basic Profile 1.0, support for SOAP Messages with Attachments is not. SwA is a significant feature of Web services practice today, however, and it's supported by J2EE Web Services, as well as a future version of the BP, version 1.1, so it's covered in Appendix E.

Once you have read Part II, you should have a pretty decent understanding of SOAP 1.1 and WSDL 1.1. If you desire more detailed knowledge, I suggest you read the Notes describing these technologies, published by the World Wide Web Consortium. You must complement that reading with study of the Basic Profile, however, because the BP imposes lots of restrictions and provides many clarifications that make SOAP 1.1 more interoperable and WSDL 1.1 more portable. Still, for most developers the level of coverage in this part of the book will be more than sufficient.