Hi Gene We are confused by the statement, "For many years we have heard how important a well-formed outcome is to process of modeling" We are unaware of any such statement - we are, of course, familiar with the so-called well-formedness conditions of outcomes in general. However, we know of no counterpart with respect to modeling. You then ask, "Would either of you explain the difference, if any, between outcome and purpose?" Again we are not aware of any particular technical use of these terms. From a natural language analysis perspective, there are many contexts in which these two terms are interchangable with no shift in truth values or, indeed, meaning. There are other verbal contexts in which there are clear differences: for example, if I say, "I have my purpose." this will have a meaning (and truth value) quite distinct from, "I have my outcome." The first is simply a statement in which the speaker is announcing that he or she has formulated a representation of what is to be accomplished. The second (on one reading) has the implication that the objective has been accomplished. All the best, Carmen and John