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Asublanguage is asubset of alanguage. Sublanguages occur innatural language, computerprogramming language, andrelational databases.
Ininformatics,natural language processing, andmachine translation, a sublanguage is the language of a restricted domain, particularly a technical domain. In mathematical terms, "a subset of the sentences of a language forms a sublanguage of that language if it is closed under some operations of the language: e.g., if when two members of a subset are operated on, as byand orbecause, the resultant is also a member of that subset".[1][2][3] This is a specific term for what in most linguistic study is referred to a language variety or register.[4]
The term sublanguage has also sometimes been used to denote a computer language that is a subset of another language. A sublanguage may be restricted syntactically (it accepts asubgrammar of the original language), and/or semantically (the set of possible outcomes for any given program is a subset of the possible outcomes in the original language).
For instance,ALGOL 68S was a subset ofALGOL 68 designed to make it possible to write a single-passcompiler for thissublanguage.
SQL (Structured Query Language) statements are classified in various ways,[5] which can be grouped into sublanguages, commonly: adata query language (DQL), adata definition language (DDL), adata control language (DCL), and adata manipulation language (DML).[6]
Inrelational database theory, the term "sublanguage", first used for this purpose byE. F. Codd in 1970, refers to acomputer language used to define or manipulate the structure and contents of arelational database management system (RDBMS). Typical sublanguages associated with modern RDBMS's areQBE (Query by Example) andSQL (Structured Query Language). In 1985, Codd encapsulated his thinking in twelve rules which every database must satisfy in order to be truly relational.[7][8] The fifth rule is known as theComprehensive data sublanguage rule, and states: