A prolog elment is an element containing metadata for a topic (for example, author, creation date, and modification date).
Example
<prolog> <author type="creator">Anna van Raaphorst</author> <copyright> <copyryear year="2007"/> <copyrholder>VR Communications, Inc.</copyrholder> </copyright> <critdates> <created date="2006-August-07"/> <revised modified="2006-August-07"/> </critdates> <metadata> <keywords> <keyword>grocery shopping</keyword> <keyword>canned goods</keyword> </keywords> </metadata> </prolog>