Undeclared entity in Docbook chapters

Hi,

 

I noticed that some Docbook projects have chapter XML files that
reference entities not declared in the chapter. The chapter will not validate
when loaded in a XML Editor and raise errors with most XML parsers. This is
usually resolved at publish time: a book XML file references those chapters
with entity variables and includes entity declaration (inline or with a link).

 

Can someone explain me the benefits (or reasons) of this
approach? Having non-validating XML files seems to defy the purpose of using XML
standards in the first place…

 

What are the alternatives for writers who want to expose and
use entities in chapters?

 

Thanks!

Fabrice