Real World XML

Using Both Internal and External DTDs

In fact, you can use both internal and external DTDs at the same time by using these forms of the <!DOCTYPE> element: <!DOCTYPE rootname SYSTEM URL [DTD]> for private external DTDs, and <!DOCTYPE rootname PUBLIC FPI URL [DTD]> for public external DTDs. In this case, the external DTD is specified by URL and the internal one by DTD.

Here's an example in which I've removed the <PRODUCT> element from the external DTD ch03_10.dtd:

 <!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 NUMBER (#PCDATA)> ...