in reply to natural language sentence construction
Tree data structures often used in natural language. Chapter 8 of Mastering Algorithms in Perl is about tree data structures, which are handled by the graph modules.
It looks like there is an AI dictionary that could be helpful in creating a useful syntax tree. You might be able to design a data structure that works like a subset of this dictionary.
Look at Damian Conway's wonderful Coy module, which is a haiku generator which is designed to create human-friendly messages. Although you aren't trying to generate haiku, you may be able to use similar programming techniques.
I think it is justified to attempt to solve such large, open problems, even if the chance of a breakthrough is small. It is a great learning experience, and you just might make a real contribution. You can also think about potential technology advances to look for in the future, so that you might be the first person to apply a newly-available technique to a difficult problem.
It should work perfectly the first time! - toma