1. A computer program product, tangibly embodied in an information carrier, the computer program product comprising instructions operable to cause data processing apparatus to perform operations comprising: 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, the artificial language being a language that has a formal definition; performing one or more word processing functions on the natural language text, the word processing functions including proofreading the natural language text for spelling, grammar, or style errors; and validating the artificial language text using one or more validation functions that are specific to the particular artificial language.