Effective XML: 50 Specific Ways to Improve Your XML

Parameterizing Attributes

Attribute declarations also benefit from parameterization. For example, the type attribute of the Transaction element can be declared as follows.

<!ENTITY % TypeAtt "type">
<!ENTITY % type.extra "">
<!ATTLIST %TransactionElement; %TypeAtt;
  (withdrawal | deposit | transfer %type.extra;)
  #REQUIRED>

Now you can change the name of the attribute by redefining the TypeAtt entity or add an additional value by redefining the type.extra entity. For example, the redefinition below adds a balanceInquiry type.

<!ENTITY % type.extra " |  balanceInquiry ">