Relax NG
ISO/IEC 19757-2:2008
application/xml
ISO/IEC 19757-2:2008 Information technology -- Document Schema Definition Language (DSDL) -- Part 2: Regular-grammar-based validation -- RELAX NG
RELAX NG by Eric van der Vlist for O'Reilly (Free Documentation Licence).
FOLiA set definition
alpha
application/xml
EBNF
ISO 14977:1996
text/plain
ISO/IEC 14977:1996 Information technology -- Syntactic metalanguage -- Extended BNF
XML Schema
1.0
application/xml
XML Schema Part 1: Structures Second Edition