There are many IDEs to create database schema pictorially. I was wondering as to how I can do it online? Are there open source codes/libraries/applications which already do this?
Basically, what i am looking at is : let the user define a table and the columns – which in common man’s term is : define relations etc pictorially.
The picture should then be translated to an xml from where i can get the relations details.
Something similar to this : http://www.zoho.com/creator/lp/easy-online-database.html
Well, zoho is not general purpose database designer, it is a cross over between CRM/ERP/Office suite and as such you are customizing the system which already holds not only table templates, but also application logic.
I don’t know of tools that would let you design visually online.
There are not too many that allow visual design in open source realm. Providing that when you say pictorially you mean E-R diagram, then take a look at this list (but none of these are online).
If you want online and if you want users(!) to be able to define the tables and columns then you will have to let users write code that will work with those tables and columns; otherwise you will not be able to give them absolute freedom.
If that is the case than you want users not to be able to define table and columns, but you want them to be able to customize existing tables (like zoho does).
Or maybe you need to look at online app/db frameworks like zope.