- #IMPLIED keyword means you can supply an attribute or not.
<!ATTLIST price currency CDATA #IMPLIED >
- If you omit the attribute, the application processing the XML data implicitly
assumes some default value
- You can specify a default to be used if the attribute is not specified
<!ATTLIST price currency CDATA "USD" >
- To state that an attribute can only be identical to a particular value:
<!ATTLIST price currency CDATA #FIXED "USD">