Controlled natural language

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Controlled natural languages (CNLs) are subsets of natural languages that are obtained by restricting the grammar and vocabulary in order to reduce or eliminate ambiguity and complexity. Traditionally, controlled languages fall into two major types: those that improve readability for human readers (e.g. non-native speakers), and those that enable reliable automatic semantic analysis of the language.

The first type of languages (often called "simplified" or "technical" languages), for example ASD Simplified Technical English, Caterpillar Technical English, IBM's Easy English, are used in the industry to increase the quality of technical documentation, and possibly simplify the semi-automatic translation of the documentation. These languages restrict the writer by general rules such as "Keep sentences short", "Avoid the use of pronouns", "Only use dictionary-approved words", and "Use only the active voice".[1]

The second type of languages have a formal syntax and formal semantics, and can be mapped to an existing formal language, such as first-order logic. Thus, those languages can be used as knowledge representation languages,[2] and writing of those languages is supported by fully automatic consistency and redundancy checks, query answering, etc.


Existing controlled natural languages include:[3][4]


IETF has reserved simple as a BCP 47 variant subtag for simplified versions of languages.[10]

See also[edit]


  1. ^ O'Brien, Sharon (2003). "Controlling Controlled English – An Analysis of Several Controlled Language Rule Sets" (PDF). Proceedings of EAMT-CLAW.
  2. ^ Schwitter, Rolf. "Controlled natural languages for knowledge representation." Proceedings of the 23rd International Conference on Computational Linguistics: Posters. Association for Computational Linguistics, 2010.
  3. ^ Kuhn, Tobias (2014). "A Survey and Classification of Controlled Natural Languages". Computational Linguistics. 40: 121–170. doi:10.1162/COLI_a_00168. S2CID 14586568.
  4. ^ Pool, Jonathan (2006). "Can Controlled Languages Scale to the Web?". Archived from the original on 2009-08-15. {{cite journal}}: Cite journal requires |journal= (help)
  5. ^ Norbert E. Fuchs; Kaarel Kaljurand; Gerold Schneider (2006). "Attempto Controlled English Meets the Challenges of Knowledge Representation, Reasoning, Interoperability and User Interfaces" (PDF). FLAIRS 2006.
  6. ^ Ogden, Charles Kay (1930). Basic English: A General Introduction with Rules and Grammar. London: Paul Treber & Co., Ltd.
  7. ^ "Common Logic Controlled English". Retrieved 27 August 2017.
  8. ^ Wasik, Szymon; Prejzendanc, Tomasz; Blazewicz, Jacek (2013). "ModeLang: A New Approach for Experts-Friendly Viral Infections Modeling". Computational and Mathematical Methods in Medicine. 2013: 320715. doi:10.1155/2013/320715. PMC 3878415. PMID 24454531.
  9. ^ Schwitter, Rolf; Tilbrook, M (2004). "PENG: Processable ENGlish". Technical Report, Macquarie University, Australia.
  10. ^ Everson, Michael. "Registration form for 'simple'". IANA. Retrieved 22 April 2021.

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