It seems the link for Download tapirtest.module is broken in this page: TAPIr: Learn by Example. Could anybody fix this?

I had already added a custom field to the uc_product table by using attribute module(an indirect way). Now I need to add another custom field only visible for system administrators, but the accessibility(or visibility) of attributes added by attribute module cannot be configured. Seems altering the uc_product table directly -- in the way discussed in this topic is the solution. Anybody can give me a further suggestion?

Thanks.