XML by Example

If all the entries that can influence the document are in the internal subset

of the DTD, the document is said to be standalone. In other words, an XML

processor does not need to download external entities to access all the infor-

mation (it might have to download external entities to validate the docu-

ment but that does not impact the content).

Conversely, if default attribute values or entities are declared in the

external subset of the document, then the XML processor has to read the

external subset, which might involve downloading more files.

Obviously, a standalone document is more efficient for communication over

a network because only one file ...