Constructing a Document Type Definition (DTD) for XML

This last type of entity represents a file, like an image or sound file, that is not XML. To declare such an entity:

    <!ENTITY ename SYSTEM "url" NDATA nname>

where ename is the name of the entity you are defining, url is the URL where the file can be found, and nname is the name of the notation that the file uses. See the section on notations below for an example.