This book is written to explain the service-oriented AJAX architecture pattern—and is not a comprehensive reference to the complete Microsoft AJAX Library, ASP.NET, and WCF. I’ll explain enough of these technologies to get you started with the pattern and make the book a readable reference. You might need to refer to MSDN documentation and use your favorite Web search engine to supplement these concepts with comprehensive reference material.

Because I’m taking an AJAX-purist approach with the service-oriented AJAX architecture pattern, I won’t include any documentation on the Update Panel. The Update Panel is a pseudo-AJAX approach that provides only some of the benefits of AJAX, but it’s primarily used to extend legacy code with AJAX-like behavior. It doesn’t fit the architectural pattern of a service-oriented framework, and it’s not something I recommend for new development. There are plenty of excellent references on the Update Panel—this book isn’t one of those.

I also don’t cover accessibility in this book. This isn’t because it’s not important—it’s very important. Frankly, there wasn’t enough time, and I’m not an expert at this. Instead, I’ll leave it to you to use the service-oriented AJAX pattern to implement accessible solutions. Because the architectural pattern implements services to provide data streams, it should be simple enough to implement alternate user interfaces that are accessible to screen readers and alternate input devices, but I will leave that to accessibility experts to document.

Next, I don’t provide a large number of usability tips in this book, even though it’s an important subject. I’ll leave it to you to take the service-oriented AJAX architectural pattern to implement usable applications. When users do something, it’s important to let them know that the system is processing their actions. If you’re loading data that may take a while, be sure to let users know that their data is loading and give them an opportunity to cancel long-running tasks.

Finally, I’m not going to cover any preview technology or betas in this book. There is a lot to anticipate, including the next version of ASP.NET AJAX (available through technology previews at www.codeplex.com/aspnet) and browser advancements, including Internet Explorer 8. Also, cross-site XML HTTP requests will be available in future browsers that will allow Web service calls to remote Web applications, whereas the pattern in this book makes Web service calls to the same Web application that hosts the JavaScript runtime and Web page.