[carstenhag]

My guess: If you are implementing any type of software, you usually see an UI, input and output. For SAP and ERP you can also have this.

But it's really ugly, messy, and you might have to implement 5 corner cases of what the german government has thought of to complicate the lives' of everyone in regards to capital gains taxes in combination with church taxes, in a year in which you got married but one of the two left the church the same year. Oh, and what if you also got a kid that year and moved cities? And during implementation there is another law passed to change stuff?

In other words: So out of the world that noone finds it interesting anymore :D