I created the Bloomberg Equity Screening (EQS) query language. It was mostly backward compatible with a previous generation, but added a lot of new things like

I created the Bloomberg Equity Screening (EQS) query language. It was mostly backward compatible with a previous generation, but added a lot of new things like chained conditionals (Python has these, most languages do not). It is meant to be familiar to users of the Excel formula language. Most users do not want to write their queries by hand, so I also built round tripping of the language to/from a GUI query builder. You can build a query graphically, edit it as text, then go back to the graphical form. Certain things cannot be displayed however, and generating good error messages was very difficult. A weird fact is that the backend which evaluates the queries has a totally different language of its own, so there is a transpiler for that. Thousands of people have used this language, but 99% of them did not know it.