Database abstraction: a abstract question

[Kevin Zembower]

I'm trying to learn about something I once saw an example of, but now can't find. I'm not even sure what to call it.

I'm setting up a database for an on-line order form. Part of the form asks what Audience the user is a member of. Choices include "Journalism," "Policymaking", etc. I understand how I can code a field such as "journalism" as an ENUM type with entries limited to "Y" or "N". This field would be part of a CUSTOMER table. An important part of the system is to generate the order form as automatically as possible, with as little manual reprogramming as possible when things like the Audience categories change.

However, I've seen other examples where the field name and type were themselves records in a table. I'm calling this another order of abstraction, but I don't know if this goes under another name. As far as I can tell, an advantage of this system is that I can add and delete Audience catagories by creating a field like "hidden" and flagging that as to whether or not the field is still to be active. This through programming then flows automatically to the order form.

My questions are:
* What's this type of concept called?
* Is there a good resource either here on this web site or on the web to learn about this technique?
* Can anyone suggest a small project that is a good example of this concept?
* Is implementing this concept a good idea, or does it add unnecessary complexity? What's the current thinking about this technique?

Thanks for all your help and suggestions.

-Kevin Zembower