In the next couple of chapters, we'll cover, at long last, what happens when we pull together all the abstract tools and strategies we've discussed and start having XML dance for us. This is the land of the XML application, where parsers all have a bone to pick, picking up documents with a goal in mind. No longer satisfied with picking out the elements and attributes and calling it a day, these higher-level tools look for meaning in all that structure, according to directives that have been programmed into it.
When we say XML application, we are specifically referring to XML-based document formats, not the computer programs (applications of another sort) that do stuff with them. You may run across statements such as "GreenMonkeyML is an XML application that provides semantic markup for green monkeys." Visiting the project's home page at http://www.greenmonkey-markup.com, we might encounter documentation describing how this specific format works, example documents, suggested uses for it, a DTD or schema used to validate GreenMonkeyML documents, and maybe an online validation tool. This content would all fit into the definition of an XML application.
This chapter looks at XML applications that already have a strong presence in the Perl world, by way of publicly available Perl modules that know how to handle them.
The term XML modules narrows us down from the Perl modules on CPAN that send mail, process images, and play ...