one of my first jobs as a developer, I had xml in everything, it grew (from the early 2000's) from just needing a configuration file that I could control the output to being used in everything. by the time of leaving that job after 18 years, my library for dealing with XML in communications from screen layouts to configuration files grew pretty vast. At the next job (never done any web dev before this) I was introduced to Json data. although, I would prefer this for communication transport if I had to go back to that old job, I would likely stay with XML for screen layouts and (some) configuration files. Json doesn't take care of everything I would like, but YAML does look interesting in how it treats object references, where two parent objects might have a common reference to a shared object. my current job has introduced me to more new concepts that I wouldn't have been exposed to in the last couple jobs. it's odd after spending so long at my first job I still think back to what I could have done better with my current knowledge.