Railroad Diagrams are used to great effect in SQLite documentation, for description of mandatory&#x2F;optional syntax elements, for example:<p><a href="https:&#x2F;&#x2F;www.sqlite.org&#x2F;lang_update.html" rel="nofollow">https:&#x2F;&#x2F;www.sqlite.org&#x2F;lang_update.html</a><p><a href="https:&#x2F;&#x2F;www.sqlite.org&#x2F;lang_createtable.html" rel="nofollow">https:&#x2F;&#x2F;www.sqlite.org&#x2F;lang_createtable.html</a><p>However the SQLite project seems to be using different tool, implemented in Tcl: <a href="http:&#x2F;&#x2F;wiki.tcl-lang.org&#x2F;21708" rel="nofollow">http:&#x2F;&#x2F;wiki.tcl-lang.org&#x2F;21708</a> .