Ellen,

My only comments are minor:

- Line 86 seems to be missing a word, or maybe has
  too many words.  You might want to take a look:

    The state of whether the execution environment
    is accepting new activities is captured the use of
                                                          ^^^^^^^

- Line 115 "in support of a execution environment"
                                   ^
                                  an

Great job.  Very helpful.

Tom