I am building a Directory and need the trade categories definitions, Ive had a look on google but havn't had much luck, I do know I want a Master Category and Sub Categories. Much like this site http://www.businesssearchnz.com/

The List I found looks to be the same as the one used in the site above to form their lists,
The List xls: http://www.nzchamber.co.nz/tradecats.asp Is under the excel Link here.

Does anyone know where a master sub of this type of list can be attain (preferably free).

And in Addition how would I construct the relationship between a listing and the categories and master categories, would this be a Recursive Relationship?

yes to your last question -- Categories and Subcategories