Parameter Entities

[beingchinmay]

Parameter entities are similar to general entities in the respect that they are also used for replacement. Parameter entities, however, are used only within a DTD. They allow for the replacement of grammar. The caveat is that parameter entities, although they can be declared within external and internal subsets, cannot be referenced within markup in the internal subset. I will return to this point in a moment. These entities may also be internal
or external, with their declarations taking the following form:

<!ENTITY % name "entity_value">
<!ENTITY % name SYSTEM "URI">
<!ENTITY % name PUBLIC "publicID" "URI">