In case you didn't know yet, a BNF grammar always is a graph. So the diagram is just a different way of depicting the same thing.

For example, the (E)BNF¹ for the graph in the article is:

  expr = term { ("+" | "-") term }

where the accolades indicate zero-or-more repetition.

This actually is important because if your grammar can be written down as a graph it means it is a context-free grammar².

Parsing is a wonderful subject to study thanks to the depth of the subject and the breath of texts available explaining it. Have fun!

¹) https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_F...

²) https://en.wikipedia.org/wiki/Context-free_grammar