My goal is to build a high quality GPX (GPS Exchange Format) in OCaml, using
the xmlm streaming code library to make the core library portable. Then build a
Unix-based layer over that to implement the IO.

The GPX homepage is at https://www.topografix.com/gpx.asp with the XSD scheme
at https://www.topografix.com/GPX/1/1/gpx.xsd and the docs at
https://www.topografix.com/GPX/1/1/