The metalanguage which is used the occasion where grammar of the language which the computer handles is defined (language in order to describe language) one.As fordefinition of computer language it is general to be described with BNF. Also Backus-Naur form and Bacchus Naur notation etc. are called.

As for BNF because with language in order to define sentence structure type, it is not something which stipulates meaning, it is not possible to define everything of language with just BNF.

Not only definition of programming language,it is use deven in protocol anddata structureand definition and the like of markup language.Most XML which has spread,thesentence structure BNF (expansion BNF) with is stipulated accur atelyas a markup language.

John Backus of the American proposed BNF in 1959, Peter Naur of the Denmark person was for the first time adopted for the definition of programming language ALGOL for numerical calculation60in1960 including correction. ... The continuation is read

Presently, the expansion BNF where it can add to original BNFexpansion(EBNF) there is many a thing which is used, butthe variety and individual expansion are many in EBNF, use which BNF it is necessary to pay attention.