I asked the problem for regular expression(the theoretical kind) for a finite set on cstheory a while ago. http://cstheory.stackexchange.com/questions/16860/mi

I asked the problem for regular expression(the theoretical kind) for a finite set on cstheory a while ago. http://cstheory.stackexchange.com/questions/16860/minimizing-size-of-regular-expression-for-finite-sets http://cstheory.stackexchange.com/questions/16860/minimizing... Apparently this problem is still open.