Refinement in State-Based Formalisms

A brief (7-page) note explaining what refinement and dummy variables are all about. It also sneaks in an introduction to TLA. In September 2004, Tommaso Bolognesi pointed out an error in the formula on the bottom of page 4 and suggested a correction. Instead of modifying the note, I’ve decided to leave the problem of finding and correcting the error as an exercise for the reader.