These simple syntactic rules make machine processing of a document relatively easy. Below is a simple example of an HTML document.
So now the book structures can be distinguished by their qualified name. This allows each book structure to be independently parsed without confusion and also allows both book structures to inhabit an enclosing document, say a catalogue of books available at different bookstores, with its own defined namespace. This latter property is an important feature because many XML documents import other vocabularies into their own documents, building up composite documents made from a variety of vocabularies.