Apache: The Definitive Guide, 3rd Edition

XML

Like HTML, Extensible Markup Language (XML) uses markup (elements, attributes, comments, etc.) to identify content within a document. Unlike HTML, XML lets developers create their own vocabularies to describe that content, encouraging a much greater separation of content from presentation. When we wrote this page, we put the chapter title at the top right hand corner of a blank page: “XML and Cocoon.” Then we started on the text:

So far we have talked about different ways of writing scripts, worrying more about the logic they contain than their content...

If you put this book down open and come back to it tomorrow, a glance at the top of the page reminds you of the subject of this chapter, and a glance at the top of the paragraph reminds you where we have got to in that chapter.

It is not necessary to explain what these typographic page elements are telling you because we have all been reading books for years in a civilization that has had cheap printing and widespread literacy for half a millennium, so we don’t even think about the conventions that have developed.

Putting the right message in the right sort of type in the right place on the page in order to convey the right meaning to the reader was originally a specialized technical job done by the book editor and the printer.

Now, computing is changing all that. We typeset our own manuscripts with the help of publishing packages. We publish our own books without the help of trained editors. We don’t have to bother with the ...