In computing, RELAX NG (REgular LAnguage for XML Next Generation) is a schema language for XML - a RELAX NG schema specifies a pattern for the structure and content of an XML document. A RELAX NG schema is itself an XML document but RELAX NG also offers a popular compact, non-XML syntax.〔(RELAX NG Compact Syntax )〕 Compared to other XML schema languages RELAX NG is considered relatively simple. It was defined by a committee specification of the OASIS RELAX NG technical committee in 2001 and 2002, based on Murata Makoto's RELAX and James Clark's TREX,〔(【引用サイトリンク】title=TREX - Tree Regular Expressions for XML - "TREX has been merged with RELAX to create RELAX NG." )〕 and also by part two of the international standard ISO/IEC 19757: Document Schema Definition Languages (DSDL).〔(RELAX NG Specification )〕〔(RELAX NG Technical Committee )〕 ISO/IEC 19757-2 was developed by ISO/IEC JTC1/SC34 and published in its first version in 2003. ==Schema examples== Suppose we want to define an extremely simple XML markup scheme for a book: a book is defined as a sequence of one or more pages; each page contains text only. A sample XML document instance might be: This is page one. This is page two.