Specifying a DTD in an XML Document

• If the DTD is more complex, it is better to store it outside the XML document
  • Use the SYSTEM keyword

    <!DOCTYPE items SYSTEM "items.dtd" >

• The resource might be an URL anywhere on the Web:

  <!DOCTYPE items SYSTEM "http://www.mycompany.com/dtds/items.dtd">

• The DOCTYPE declaration can contain a PUBLIC keyword

  <!DOCTYPE faces-config PUBLIC
     "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN"
     "http://java.sun.com/dtd/web-facesconfig_1_0.dtd">

  If the public identifier is familiar, the program parsing the document need not spend time retrieving the DTD