Database help

I need some help with a few things in regards to documenting a database. What need to do is create a data dictionary. I don’t know how to start it. If anyone has done it before I please share some ideas. I am also supposed to do the data dictionary in html and also put in rdf tags. I understand how to write html and the rdf, but I really don’t understand what the purpose of the rdf is and how it effects the html doc.

Someone hook a brother up.