update graphics that describe NXDL structures

[prjemian]

The graphics displayed in the manual to describe the structures in nxdl.xsd are out of date. They were generated automatically by a commercial program. Create tools that use open-source software to update these graphs on demand (not with every build of the manual). GraphViz is one example of open-source Python code to build directed graphs.

[prjemian]

example: http://download.nexusformat.org/doc/html/nxdl_desc.html#attribute

[prjemian]

Are these graphics even useful to anyone? If it is not possible to update them as the standard evolves, they become a source of wrong information.

I recommend deprecating these graphics in the documentation (not updating them now) and removing them from the documentation in a future release such as 2021-10.

[benajamin]

I agree that the graphics in the manual are in dire need of a complete overhaul. This should be a major topic for the next code camp.