On useful error messages.

Dear Developers (of any software),

Just a little note to request that you contemplate your error messages more carefully, specifically while it’s a good idea to validate data and assume its hostile, think about the message you want to send to your users.

To use an example that annoyed me today – examine the Pizza Hut online ordering system – if you live in an area where the local store does not accept online orders – the system does not tell you this. It rejects the post code as invalid – the problem is that the error is wrong. The post code is a valid Australian postcode. The system should instead report back the actual problem – the store in your area does not accept online orders please call 13 11 66 or similar.

This is a problem with a great deal of software – developers need to remember that software is destined to be used by people, and that any error messages generated should be meaningful to the end user. From the perspective of the software as in the example above the post code is invalid, but as an end user – it is not, it is a valid postcode as per the definition of a post code. So all you developers out there think about your error messages, yes its not fun to handle many cases (for the above – they would need to handle both invalid postcodes as well as valid post codes but not in a serviced area). Your end users will be happier with the software.