Book is the parent element of both title and chapter. Elements have Content Elements can have different content types. An element can have element content, mixed content, simple content, or empty content. An element can also have attributes . In the example above, book has element content , because it contains other elements.
Chapter has mixed content because it contains both text and other elements.
Prod has empty content , because it carries no information. In the example above only the prod element has attributes . Names with an underscore separator are nice. Element names can be as long as you like, but don't exaggerate. XML documents often have a corresponding database, in which fields exist corresponding to elements in the XML document.