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Inside XML by Steven Holzner

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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 order.dtd for this document:

 <?xml version = "1.0" standalone="no"?> <!DOCTYPE DOCUMENT SYSTEM "order.dtd"> <DOCUMENT> <CUSTOMER> <NAME> <LAST_NAME>Smith</LAST_NAME> <FIRST_NAME>Sam</FIRST_NAME> </NAME> <DATE>October 15, 2001</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> <PRODUCT>Lettuce</PRODUCT> ...

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