One of my very, very, very first jobs (1999) was at a startup that was leaning very heavily into XML for dealing with structured data. A massive amount of time

One of my very, very, very first jobs (1999) was at a startup that was leaning very heavily into XML for dealing with structured data. A massive amount of time was spent dealing with issues related to hand-editing XML, so I went deep into building schemas, utilities to validate XML according to the schema, and finally building an editor that was capable of providing some XSD-enabled automagic. Good times.