New Techniques for Proving the Decidability of Equivalence Problems

We will discuss severai recentI) developed :e_h.ci;ues for prcving the decidability of the equivalence problem for devices den #III& languages and relations. Most of these techniques come from the development originat,d 1;1 the proof of the decidability of the DOL equivalence problem. Of particular importance is c.te recently shown validity of the Ehrenieucht conjecture and its effective variations.