XML is remarkably flexible. If you don't use a DTD, you can create a document using almost any kind of structure you want. You might choose to represent a person's name through attributes:
<person first-name="Samantha" last-name="Tippin">
Or, you might create separate tags for the various data items associated with a person:
<person> <first-name>Samantha</first-name> <last-name>Tippin</last-name> </person>
Flexibility, of course, is a two-edged sword. Because you are able to format your data how ever you like, it's unlikely you'll use the same format as someone else. A Document Type Definition enables you to define a specific format for an XML document. You can specify which tags might appear in a ...