However, we're getting ahead of ourselves. In order to map one message format or structure to another, to translate its contents for example, we first need to understand the messages themselves. Fundamental to this is schema.

BizTalk Services differentiates between two types of messages: XML and non-XML. All XML message formats are expressed using XSD, and all non-XML message formats are expressed using XSD. So, XSD is important! The purpose of this book is not to provide a primer in XSD; we'll refer to other references if you need some background on the technologies we mention. Instead, we'll provide just enough to show how BizTalk Services uses such technologies so that the less familiar can still understand what is going on.

Now, you're probably wondering how any message formats you can think up can be defined in XSD. Let's look at an example.