Two confessions: Number one: I am a bit of a systems engineering geek. Number two: I love Mary Poppins. If you have a kid (or even if you don’t) and you haven’t seen Mary Poppins, then shame on you. Get on it.
While watching Mary Poppins for the nth time, I suddenly realized the wonderful example of a system engineering lifecycle that’s built into the first act of the movie.
Trust me; I am not wasting your time! But just in case, I've made a clip so you can watch all of the relevant scenes in just a few minutes (and hopefully whet your whistle to see the whole movie).
The first lesson that the movie highlights is the difference between buyer requirements and user requirements. We tend to think of them as being the same, but for many products, we can easily differentiate between the two (as a dad who has taken his teenage daughter clothes shopping, I assure you that the buyer and user requirements can be at odds). In this case, Mr. and Mrs. Banks decide to place an ad for a new nanny. We know that these are requirements, because as Mr. Banks picks up the phone and asks for the London Times, he begins his advertisement by stating, “Wanted – no, required….,” and then proceeds to list the design and performance requirements for the nanny.
However, shortly thereafter, Jane and Michael come down with a list of their written user requirements. It’s important to note that Jane and Michael’s requirements are significantly different than the buyer’s requirements as elucidated by Mr. Banks.
Here is the important part: Considering the concept of operation of this “system, we can see that the two requirement sets are actually complementary. What is the role of the nanny? We can infer that it is to raise Jane and Michael to be good people. Mr. Banks has his requirements which he feels will yield that result, as do Jane and Michael. Two different requirement sets with the same goal are not necessarily contradictory (although in this case, Mr. Banks could not disagree more.)
One common occurrence during the design process is that the end user may not be impressed with the initial system concepts. As we know, the design process is iterative, and the initial concepts, although providing the required capability, may not meet the users qualitative or aesthetic (technical and/or physical) needs.
However, the design process is iterative and eventually a preferred system concept is selected, in this case none other than Mary Poppins.
When Mary Poppins actually meets George Banks, she begins the requirements verification process.
“You are George Banks?”
“You do live at this address?”
“You did place an advertisement?”
I chuckle when Mary says, “Rosy cheeks: obviously.” (For those of you are paying attention, this is verification by inspection.) As she goes through Jane and Michael’s list of requirements, point by point, she states how each requirement is verified by her persona. Once Mary has concluded her review of the requirements, she defines the Operational Test and Evaluation (OT&E) period of performance needed to achieve customer validation: one week.
Then Mary departs to go up to the children’s room. It’s worth noting that when Mrs. Banks comes into the room, she speaks in the language of system validation. “Is she the one? Will she mold and shape our children?” In other words, “is this the right system?” She is not focused simply on the requirements (verification), but on the overall need that must be met. To which Mr. Banks responds, “Yes, I believe she will.”
So there you have it; basic systems engineering as taught by Mary Poppins. And after you’ve watched this part of the movie, I suggest you watch the rest of the movie.
Because frankly, it’s a really good movie.