DiagramOfEffects

A Diagram of Effects is a tool for reasoning about non-linear systems. The main difference with system roadmaps is that the emphasis is on the detection and further investigation of feedback loops.

The in this page used description of Diagram of Effects was adapted from Appendix A of the first book in Quality Software Management series of JerryWeinberg: http://www.geraldmweinberg.com/books.html, for which Jerry graciously gave his permission because of the example used: “I always give my permission for fairy tales”.

This tale is from a theme in The Once and Future King written by T. H. White

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"Look over there." "The Wart looked and at first saw nothing. Then he saw a small translucent shape hanging motionless near the surface. It was just outside the shadow of a waterlily and was evidently enjoying the sun. It was a baby pike, absolutely rigid and probably asleep and it looked like a pipe stem or a seahorse stretched out flat. It would be a brigand when it grew up.

"I am taking you to see one of those," said the tench, "the Emperor of these purlieus. As a doctor I have immunity, and I daresay he will respect you as my companion as well - but you had better keep your tail bent in case he is feeling tyrannical." "Is he the King of the Moat?" "He is. Old Jack they call him, and some call him Black Peter, but for the most part they do not mention him by name at all. They just call him Mr. P. You will see what it is to be a king."

The Wart began to hang behind his conductor a little, and perhaps it was well that he did, for they were almost on top of their destination before he noticed it. When he did see the old despot he started back in horror, for Mr. P. was four feet long, his weight incalculable. The great body, shadowy and almost invisible among the stems, ended in a face which had been ravaged by all the passions of an absolute Monarch -by cruelty, sorrow, age, pride, selfishness, loneliness and thoughts too strong for individual brains. There he hung or hoved, his vast ironic mouth permanently drawn downward in a kind of melancholy, his lean clean-shaven chops giving him an American expression, like that of Uncle Sam. He was remorseless, disillusioned, logical, predatory, fierce, pitiless -but his great jewel of an eye was that of a stricken deer, large, fearful, sensitive and full of griefs. He made no movement, but looked upon them with his bitter eye.

The Wart thought to himself that he did not care for Mr.P.

"Lord," said Merlyn, not paying attention to his nervousness, "I have brought a young professor who would learn to profess." "To profess what?" asked the King of the Moat slowly, hardly opening his jaws and speaking through his nose. "Power," said the tench. "Let him speak for himself." "Please," said the Wart, "I don't know what I ought to ask." "There is nothing," said the monarch, "except the power which you pretend to seek: power to grind and power to digest, power to seek and power to find, power to await and power to claim, all power and pitilessness springing from the nape of the neck." "Thank you." "Love is a trick played on us by the forces of evolution. Pleasure is the bait laid down by the same. There is only power. Power is of the individual mind, but the mind's power is not enough. Power of the body decides everything in the end, and only Might is right"

A diagram of effects consists primarily of nodes connected by arrows:

1. Each node stands for a measurable quantity, like Grind and Digest, Seek and Find or Await and Claim. The nodes having a “cloud” form serves as a reminder that nodes indicate measurements, not things or processes as in flowcharts, data flow diagrams, and the like.

2. The cloud nodes can represent either actual measurements or conceptual measurements –things that could be measured at present because they may be too expensive to measure or not worth the trouble, or just not measured yet. The important thing is that they can be measured.

3. To indicate an actual measurement currently being made, use a regular, elliptical cloud. Most of the time, however, effects diagrams are used for conceptual –rather than mathematical– analysis, so most of the clouds will be appropriately rough.

4. An arrow from node A to node B indicates that quantity A has an effect on quantity B. We may know or deduce the effect that leads us to draw the arrow in one of three ways:

• From a mathematical formula as in NetworkFlowMath for describing the effect
• Deduced from observations, for instance, when people are observed to get nervous and lose their effectiveness when under pressure from management;
• Inferred from past experience, for instance noticing the change in our bodies demand for food when time is spent on making love or new meanings.

5. The general direction of the effect of quantity A on quantity B may be indicated by the presence or absence of the large gray dot on the arrow between them.

• No dot means that as A moves in one direction, B moves in the same direction like when spending time on Seek and Find, Wait and Claim, Grind and Digest, one’s body will grow by a proportionate amount.
• A dot on the arrow means that as A moves in one direction, B moves in the opposite direction like when spending time on Seek and Find, Wait and Claim, Grind and Digest, one is not spending that time on Making Love.
• A mathematical formula as in NetworkFlowMath for describing the transformation
• Deduced from observations, for instance, when people are observed to get nervous and lose their effectiveness when under pressure from management inferred from past experience, for instance noticing the change in our bodies demand for food when time is spent on making love or new meanings.

6. A square on an effects line indicates that human intervention is determining the direction of the effect:

• A white square means that human intervention is making the affected measurement move in the same direction as the movement of the cause (just as a plain arrow indicates a natural same direction).
• A gray square means that human intervention is making the affected measurement move in the opposite direction as the movement of the cause (just as a gray dot indicates a natural opposite direction)
• A half-white/half gray square means that human intervention can make the affected measurement move in the same or the opposite direction as the movement of the cause, depending on the intervention. In our case Mr.P can choose to investigate other causes by trying other behavior.

"Now I think it is time that you should go away, young master, for I find this conversation uninteresting and exhausting. I think you ought to go away really almost at once, in case my disillusioned mouth should suddenly determine to introduce you to my great gills, which have teeth in them also. Yes, I really think you might be wise to go away this moment. Indeed, I think you ought to put your back into it. And so, a long farewell to all my greatness."

The Wart had found himself almost hypnotized by the big words, and hardly noticed that the tight mouth was coming closer and closer to him. It came imperceptibly, as the lecture distracted his attention, and suddenly it was looming within an inch of his nose. On the last sentence it opened, horrible and vast, the skin stretching ravenously from bone to bone and tooth to tooth.

Inside there seemed to be nothing but teeth, sharp teeth like thorns in rows and ridges everywhere, like the nails in labarours' boots, and it was only at the last second that he was able to regain his own will, to pull himself together, to recollect his instructions and to escape. All those teeth clashed behind him at the tip of his tail, as he gave the heartiest jack-knife he had ever given. In a second he was on dry land once again, standing beside Merlyn on the piping drawbridge, panting in his stuffy clothes.

-- NynkeEtkFokma, 2002