Migration

Hi, Everyone

I'm new to this list. I'm not sure whether the following question has 
been asked.

I'm planning to migrate out from DTD to XML Schema on some of our XML files.
However, I cannot find the equivalent of the DTD Entity declaration in 
XML Schema, or is there?

So does it mean that I can only convert the element and attribute schema 
from DTD to XML Schema, and still have to leave entity declarations in DTD?

Henry