Inside XML

Creating Document Type Definitions

To introduce DTDs, I'll start with a DTD that's internal to the document whose syntax it specifies (we'll see how to create external DTDs later in the chapter). In this case, the DTD itself goes inside the square brackets in <!DOCTYPE> (note that I've set the standalone attribute to "yes" here because this document doesn't rely on any external resources):

 <?xml version = "1.0" standalone="yes"?> <!DOCTYPE DOCUMENT [ <!ELEMENT DOCUMENT (CUSTOMER)*> <!ELEMENT CUSTOMER (NAME,DATE,ORDERS)> <!ELEMENT NAME (LAST_NAME,FIRST_NAME)> <!ELEMENT LAST_NAME (#PCDATA)> <!ELEMENT FIRST_NAME (#PCDATA)> <!ELEMENT DATE (#PCDATA)> <!ELEMENT ORDERS (ITEM)*> <!ELEMENT ITEM (PRODUCT,NUMBER,PRICE)> <!ELEMENT PRODUCT (#PCDATA)> <!ELEMENT ...