Reviewing models, be it in academic exercises, of full-blown\u00a0industrial designs and architectures, or as part of scientific\u00a0research, is quite hard and it is non-obvious what good criteria for\u00a0such an evaluation could be. Here is a story of a \u201cmodel review\u201d, told by Richard P. Feynman, in which\u00a0he is considering a blueprint of a chemical plant (\u201cSurely You\u2019re Joking, Mr. Feynman!\u201d, Vintage, 1992, pp. 123sqq.):<\/p>\n
How do you look at a plant that isn\u2019t built yet? I\u00a0don\u2019t know. Lieutenant Zumwalt [\u2026] takes me into this\u00a0room where there are these two engineers and a loooooong<\/em>\u00a0table covered with a stack of blueprints representing the various\u00a0floors of the proposed plant.<\/p>\n
I took mechanical drawing when I was in school, but I am not good\u00a0at reading blueprints. So they unroll the stack of blueprints and\u00a0start to explain it to me, thinking I am a genius. Now, one of the\u00a0things they had to avoid in the plant was accumulation. They had\u00a0problems like when there\u2019s an evaporator working, which is\u00a0trying to accumulate the stuff, if the valve gets stuck or something like that and too much stuff accumulates, it\u2019ll explode. So they\u00a0explained to me that this plant is designed so that if any one valve\u00a0gets stuck nothing will happen. It needs at least two valves\u00a0everywhere.<\/p>\n
Then they explain how it works. The carbon tetrachloride comes in\u00a0here, the uranium nitrate from here comes in here, it goes up and\u00a0down, it goes up through the floor, comes up through the pipes, coming\u00a0up from the second floor, bluuuuurp<\/em>\u2014going through the\u00a0stack of blueprints, down-up-down-up, talking very fast, explaining\u00a0the very very complicated chemical plant.<\/p>\n
I\u2019m completely dazed. Worse, I don\u2019t know what the\u00a0symbols on the blueprint mean! There is some kind of a thing that at\u00a0first I think is a window. It\u2019s a square with a little cross in\u00a0the middle, all over the damn place. I think it\u2019s a window, but
\nno, it can\u2019t be a window, because it isn\u2019t always at the\u00a0edge. I want to ask them what it is. [\u2026]\u00a0I get an idea. Maybe\u00a0it\u2019s a valve. I take my finger and I put it down on one of the\u00a0mysterious little crosses in the middle of one of the blueprints on\u00a0page three, and I say \u201cWhat happens if this valve gets stuck?\u201d \u2014figuring they\u2019re going to say, \u201cThat\u2019s not a\u00a0valve, sir, that\u2019s a window.\u201d<\/p>\nSo one looks at the other and says, \u201cWell, if that<\/em> valve gets stuck\u2014\u201d and he goes up and down on the blueprint, up and down, the other guy goes up and down, back and forth, back and forth, and they both look at each other. They turn around to me and they open their mouths like astonished fish and say \u201cYou\u2019re absolutely right, sir.\u201d<\/p><\/blockquote>\n
Looking at the story from a more general model review perspective, the fundamental model properties of mapping, reduction, and pragmatism coined by Herbert Stachowiak (\u201eAllgemeine Modelltheorie\u201c, Springer, 1973) may be a first start. The blueprints seem to have worked rather well in this respect: The mapping in the blueprints made it possible to review a plant that had not been built yet, though, in fact, the mapping was not clear to all reviewers (and it is not told whether the plant could have been constructed successfully from these blueprints). The blueprints were pragmatically successful, i.e., the model was apt for the purpose of analysing whether only one valve getting stuck could lead to accumulation. However, heavy explanation was necessary, and still some mistakes could go undetected. It may be speculated that the\u00a0reduction for the ultimate goal of fault analysis could have been more elaborate.<\/p>\n
Are there other criteria that should be considered when reviewing a model? Maybe originality and novelty would be of some importance, in particular judging whether the
right<\/q> reduction has been chosen for some intended pragmatic purpose. But would for example also aesthetic criteria count? Or the (mis-)use of some arcane modelling language feature?<\/p>\n","protected":false},"excerpt":{"rendered":"Reviewing models, be it in academic exercises, of full-blown\u00a0industrial designs and architectures, or as part of scientific\u00a0research, is quite hard and it is non-obvious what good criteria for\u00a0such an evaluation could be. Here is a story of a \u201cmodel review\u201d, told by Richard P. Feynman, in which\u00a0he is considering a blueprint of a chemical plant … Continue reading Model Review Criteria<\/span>