Methods and apparatus, including computer program products, implementing techniques for word processing. The techniques include receiving a word processing document that includes natural language text, identifying in the word processing document a segment of artificial language text that is written in a particular artificial language, performing one or more word processing functions on the natural language text, and validating the artificial language text using one or more validation functions that are specific to the particular artificial language. The artificial language is a language that has a formal definition. The word processing functions including proofreading the natural language text for spelling, grammar, or style errors.