A Survey and Classification of Controlled Natural Languages
This work provides a common framework for researchers and developers in natural language processing and formal logic, but it is incremental as it synthesizes existing knowledge rather than introducing new methods.
The paper tackles the problem of diverse terminology and lack of unified understanding in controlled natural languages (CNLs) by presenting a comprehensive survey and classification of 100 English-based CNLs from 1930 to the present, revealing they form a continuum between natural and formal languages.
What is here called controlled natural language (CNL) has traditionally been given many different names. Especially during the last four decades, a wide variety of such languages have been designed. They are applied to improve communication among humans, to improve translation, or to provide natural and intuitive representations for formal notations. Despite the apparent differences, it seems sensible to put all these languages under the same umbrella. To bring order to the variety of languages, a general classification scheme is presented here. A comprehensive survey of existing English-based CNLs is given, listing and describing 100 languages from 1930 until today. Classification of these languages reveals that they form a single scattered cloud filling the conceptual space between natural languages such as English on the one end and formal languages such as propositional logic on the other. The goal of this article is to provide a common terminology and a common model for CNL, to contribute to the understanding of their general nature, to provide a starting point for researchers interested in the area, and to help developers to make design decisions.