Re: [xml-dev] It is okay for things to break in the future!

[Michael Kay <mike@saxonica.com>]

> 
> This is a really, really common mistake made by inexperienced developers - we used to see this all the time in phone number formats, for example. Then mobile numbers came along and changed the formats. And international phone calls became really common, necessitating country codes as a standard part of phone numbers. Etc etc etc :)
> 

I have had to invent an imaginary US phone number before now in order to get past such stupid validation rules.

A golden rule of validation - never force your users to enter incorrect data in order to get past your validation rules!

Another case I enountered was where the system had a minimum age for employees of 16, but many countries allow you to employ 15-year olds. So they got around it by entering an incorrect date of birth. Validation is there to improve the data quality, not to make it worse!

Michael Kay
Saxonica