Hamilton--The Great Schema of Things

Now for the bad news. Although XML can do all those wonderful things and many more, it requires what is known as a Document Type Definition (DTD) or schema to drive a computer-integrated manufacturing system. This is where the devil lies in the details.

Like any language, the value is proportional to the number of people who understand it. And DTDs are the dictionaries, if you will, that enable people and systems to understand what is meant by the XML constructs so they can interpret and process the actual data files. And while DTDs are in the public domain, residing somewhere within the server bowels of the World Wide Web Consortium, they still must be written and maintained, and the new ones must jive with existing ones.