External Parameter Entities
When you use a parameter entity in the DTD's external subset, you can reference that entity anywhere in the DTD, including in element declarations. Here's an example. In this case, I'm using an external DTD named ch04_07.dtd for this document:
<?xml version = "1.0" standalone="no"?>
<!DOCTYPE DOCUMENT SYSTEM "ch04_07.dtd"> <DOCUMENT> <CUSTOMER> <NAME> <LAST_NAME>Smith</LAST_NAME> <FIRST_NAME>Sam</FIRST_NAME> </NAME> <DATE>October 15, 2003</DATE> <ORDERS> <ITEM> <PRODUCT>Tomatoes</PRODUCT> <NUMBER>8</NUMBER> <PRICE>$1.25</PRICE> </ITEM> <ITEM> <PRODUCT>Oranges</PRODUCT> <NUMBER>24</NUMBER> <PRICE>$4.98</PRICE> </ITEM> . . . <ITEM> <PRODUCT>Asparagus</PRODUCT> <NUMBER>12</NUMBER> <PRICE>$2.95</PRICE> </ITEM> <ITEM> ...Get Real World XML now with the O’Reilly learning platform.
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