In such a case the right way to go is to build a formal model of the informal expectations first. I.e., split scientific and engineering phases. Collect your data, build a theory, validate it, and only then engineer an implementation of it, mechanically, with zero mental activity.

And what you seem to suggest, start writing a parser and then experiment with various real-world inputs until you're satisfied, is certainly not a very productive way of doing things.

I'm not suggesting anything but that you can't build it from first principles. Collecting data and building a theory is not working from first principles, it's just a more structured way of hacking it until it works. You're still liable to have the next website you crawl break your parser.

> but that you can't build it from first principles

Do not confuse principles (which are universal, simple and beautiful) with specs (which suck shit a metric ton per second).

> it's just a more structured way of hacking it until it works

You're confusing hacking with cargo cult coding. Hacking until it works is exactly this formal loop: collect the data, build a model, test if it's applicable. Cargo cult is "google for an answer, paste some code from stackoverflow, see if it works". The OP article is about the latter.