Here is a book dedicated to one of the most promising markup languages ​ ​ - XML. In this book, you will learn what markup languages ​ ​ are in general, what are correct and valid XML documents, as well as the schemes used to check them. In addition, the book discusses XML namespaces, XPath, XLink, XPointer and XSL languages, the use of DOM and SAX to process XML documents, and the use of style sheets. A separate part contains various issues related to the practical use of XML, for example, in e-commerce. The book is designed for users with different levels of training.