extended Back-Naur Form notation

XDRの拡張済BNF

[2] RFC 1014 - XDR: External Data Representation standard, https://datatracker.ietf.org/doc/html/rfc1014#section-5

[3] RFC 1832 - XDR: External Data Representation Standard, https://datatracker.ietf.org/doc/html/rfc1832#section-5.1

[1] RFC 4506: XDR: External Data Representation Standard, , https://www.rfc-editor.org/rfc/rfc4506.html#section-6.1

an extended Back-Naur Form notation