XML in a Nutshell, 3rd Edition

Narrative Document Structures

All XML documents are trees. However, trees are very general-purpose data structures. If you’ve been formally trained in computer science (and very possibly even if you haven’t been), you’ve encountered binary trees, red-black trees, balanced trees, B-trees, ordered trees, and more. However, when working with XML, it’s highly unlikely that any given document matches any of these structures. Instead, XML documents are the most general sort of tree, with no particular restrictions on how nodes are ordered or how or which nodes are connected to which other nodes. Narrative XML documents are even less likely than record-like XML documents to have an identifiable structure beyond their mere treeness.

So what does a narrative-oriented XML document look like? Of course, there’s a root element. All XML documents have one. Generally speaking, this root element represents the document itself. That is, if the document is a book, the root element is book. If the document is an article, the root element is article, and so on.

Beyond that, large documents are generally broken up into sections of some kind, perhaps chapters for a book, parts for an article, or claims for a legal brief. Most of the document consists of these primary sections. In some cases, there’ll be several different kinds of sections; for instance, one for the table of contents, one for the index, and one for the chapters of a book.

Generally, the root element also contains one or more elements ...