XML by Example

Parameter entities have many applications. You will learn how to use para-

meter entities in the following sections: “Internal and External Entities,”

“Conditional Sections,” “Designing DTDs from an Object Model.”

CAUTION

The previous example is valid only in the external subset of a DTD. In the internal sub-

set, parameter entities can appear only where markup declaration can appear.

Internal and External Entities

XML also distinguishes between internal and external entities. Internal

entities are stored in the document, whereas external entities point to a

system or public identifier. Entity identifiers are identical to DTD identi-

fiers (in fact, ...