Modelling tends to focus on what’s specific to your domain, which means starting from the beginning, all the way down to the level of individual number and text values. But data such as telephone numbers and people’s names have been around for longer than computers, and don’t need modelling all over again. Reinventing models for these universal values leads to weak models that don’t accommodate real-world complexity, and fail to benefit from international standards.Everyone involved in detailed software design needs to know what telephone numbers, house numbers and aircraft tail numbers have in common. Attendees will discover different kinds of numbers, learn about validating email addresses and bank account numbers, and realise how unoriginal some of their bugs are. And more important than bugs that are easy to fix, we’ll see why modelling with familiar data can lead to software that fails to be inclusive.