<i>&gt;Does not involve railroads :&#x2F;</i><p>Couldn&#x27;t tell if you were joking but &quot;railroad&quot; is a common term-of-art for syntax diagrams.  
Example:  <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Syntax_diagram" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Syntax_diagram</a>