[Zope] Info about a Z Gadfly Database in a DTML doc

Hello zopers, I'm new in Zope, and i can't deal with that : how can i reach informations about tables from a Z Gadfly Database Connection? For example, using the 'Sample Gadfly script' from a Zope How-to, how can i get the fact that the 'Zopadelic' base has one table, 'zopista', which has 2 columns (col_a and col_b) from the int type ? Of course i can get that info with the browse tab, but my need is to get that from a DTML document (which will be the beginning of a little web interface for Gadfly i hope.) I read the docs and didn't find the answer, do i have to code a external method? Hope this is clear, i'm not sure of my english ;) Guillaume Gautier