natural language preprocessor

I am working on a natural language preprocessor, possibly for use with Asa H.  The simplest version forces you to use only words that the AI knows.  It compares each word that is input to a vocabulary listing of all the words the AI understands.  A more complex version of the preprocessor would allow the use of words that are synonyms of the words the AI understands.  This would involve augmenting the AI's vocabulary listing by adding synonyms.  A still more complex preprocessor would search for phrases in the input and compare these with synonym phrases.  Again, the vocabulary listing would be expanded to include the phrases that the AI understands and sets of synonym phrases. A spell checker may also be useful.