Arbortext Editor 5.4 and IsoDraw 7.3?

With the feature in Isodraw 7.3 of being able to link a hotspot with data in an XML file I have been asked a question. The user wants to know "Is there a specific schema the XML must adhere to?" .

Since I work on the graphics and not the SGML I do not know the answer so I am hoping someone here can answer this so I can pass it on.

Thanks for your help,

Keith