When appropriate data controls are not used, data structure need to be changed based on the user requirements. Based on the code/program written in data structure, the corresponding controls can be made enable and perform interaction between user and design interface.

For example, fig (1) (a) presents are a for the seller to enter the details of her furniture, here, the seller to enter, the details of his/her furniture.

Here, the seller free to describe everything in is/her own words. All the fields such as pick-up location, type of furniture, price and contact details are mandatory.