Subject: Re: Wegner
From: "William J. Rapaport" <rapaport@buffalo.edu>
Date: Mon, 12 Apr 2010 08:57:24 -0400 (EDT)

You may recall that a student wrote:
"I am reading the article by Wegner, and he wrote that Milner, in 1975,
noticed that concurrent processes cannot be expressed by sequential
algorithms. But I thought that it was proven that sequential processing
can simulate parallel processing. Am I mistaken?"

Here's another reply:
Prof. Shapiro has suggested to me in conversation that an activity that
would require two actions to be carried out in parallel--i.e.,
simultaneously--might not be simulatable sequentially (though perhaps the
activity could be accomplished in some other fashion). E.g., suppose it
requires two hands behaving in parallel to carefully lift a pot off the
stove. Simulating that sequentially, first with one hand, then with the
other, just won't do it.