This week, I received an interesting task: dusting off a legacy Java application. The application analyzes specific XML files in proprietary format. I know XML doesn’t sound sexy to junior developers, but it has an amazing benefit. One can validate a file against a grammar. Such grammar is called an XSD, the acronym for XML Schema Definition. Fun fact: you write XSDs in XML. In this post, I explain the problem, what I tried, and the final working solution.