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Written by Steven Bussey
on February 20, 2020

Controlled language is a subset of natural language with a restricted grammar and vocabulary that reduces or eliminates ambiguity and complexity.

Everyone uses natural language in daily communication with friends, family and co-workers. Natural language is what human beings use to communicate with each other and is created over a long period of time. However, its informal usage rules and many layers of cultural nuance and meaning create problems for both non-native speakers of that language and machines. Controlled language helps solve these problems. It is a restricted form of a language characterized by simplified grammar and limited vocabulary.


Examples of controlled language

Basic English – The most famous controlled language for human communication is Basic English, which was created in the 1930s to help non-native speakers to learn English quicker. Basic English derives its vocabulary and grammar from Standard English, but eliminates most words (in particular verbs), and mandates only simple grammar rules. The core vocabulary of Basic English consists of about 850 words. A modified form of Basic English, known as Simple English, is used on Simple English Wikipedia, which is a version of Wikipedia designed for children and learners of English.

Simplified Technical English – ASD Simplified Technical English (ASD-STE100) is a controlled language with a narrower focus than Basic English or Simple English. It was created for the aerospace industry to help readers easily understand maintenance documentation. Most technical materials used in multinational aerospace companies is written in English, while many readers have only limited knowledge of the language.

ASD-STE100 includes a set of about 60 writing rules and a basic vocabulary of about 870 approved words. The words were chosen for their simplicity and ease of recognition. There is only one part of speech and one meaning for each word. For example, the word ”test” is approved as a noun but not as a verb, and the verb ”follow” has an approved meaning of ”come after”, but not ”obey”. ASD-STE100 has been adopted by other industries for technical documentation including defense, construction and medicine.

Machine Translation – Controlled language improves the quality of Machine Translation. In most cases, MT output requires a degree of human checking and post-editing. The rationale for using controlled language in MT is to limit ambiguity and complex sentence structures in the source language to achieve better translation results and reduce the need for human involvement. This lowers the costs and improves the quality of translation.


Benefits of controlled language

Controlled languages allow authors to produce documents that are easily read, comprehended and retained. They are also more consistent in terms of vocabulary and style, at the price of less creative freedom. Other advantages are:

  • They reduce the number of support incidences thanks to being more readable and comprehensible;
  • They allow to automate routine editing tasks and employ objective quality metrics for a better authoring process;
  • They help produce uniform and standardized source documents, which increases the translation memory match rate and lowers translation costs;
  • It is faster and cheaper to build Machine Translation engines for texts written in controlled language and the quality of translation is higher.

Controlled language is most suitable for:

  • Software strings
  • Help & support articles
  • Technical specifications and documentation

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