Designing data entry for a system

How do you work out what data you need to capture for a system? This is a question not often asked, at least not in the right way. Designing data entry for a system should be driven by the wants and needs of the output. It’s no good gathering data if it’s never going to be used, or if it is in the wrong format for the required output.

Examples of incorrect data entry

To put this into perspective, consider these;

• You have postal system that prints address labels. This requires that the address fits into a box of limited size. However, the source data can be any size, with multi-line addresses recorded in plain text. Which part is the Zip code/postal code?
• You need to report on customers from multiple sources, sorted by family name. However, sources have names in multiple varying formats such as Last, First and First M. Last in single fields. You will need to use some middleware to transform those data points.
• You need to list the delivery date for all products in stock, however your system only recorded ordering date. How can you evaluate supplier performance if you are not gathering all required fields?

You have to put in what you want to get out

Going further than the adage of “rubbish in, rubbish out” for content, you need to consider the type of information you need or want – in the [grossly over simplified] examples above, delivery dates need to be entered if you want to be able to report on them.

If it’s coming out and you don’t want it, don’t put it in

Conversely, if a database has been created to gather data that is never used (and is not required for regulatory reasons), then don’t gather it! We’ve all experienced systems where you need to fill in a form [online] that requests data that you know will never be needed or used – and the form marks these fields as compulsory!

System Design poster

I’ve created a simple poster to illustrate this. I hope it helps you when you are designing a system.

I’ve made this into a PDF, feel free to distribute, provide a link to this page when distributing please.
http://v-wiki.net/files/System_Design_Poster.pdf