What software design pattern to use for a propositional logic system? [on hold]

I'm about to develop a web-based propositional logic system where a user enters an equation and the system validates the equation and outputs the truth table if it is correct , with addition to minor services such as sending the truth table to the signed in user via E-mail.

And it might contain converting equations from PL to PL' for example.

What software engineering design pattern suits a system like this best ?