Choosing the Diagram

All six diagram typesPart V · Pattern and Judgment · Chapter 12 of 12 · the closing chapter

Which diagram, if any, answers your question? Each of the six diagram types answers its own kind of question, so you may draw several for one situation, and none for a question arithmetic answers.

Print this chapter, with a sheet for each exercise and the answers at the back, from its PDF.

Ana’s two hives

Ana keeps two colonies of honey bees in her garden. She sells honey, the farm next door sprays its crops, and a bee inspector calls. Her questions:

Whom do I deal with, and what passes each way?
What bears on the honey I harvest?
Why does a growing colony swarm?
How much honey can I take and still leave enough?
How do I keep each hive heavy enough for winter?
Have I seen this story before?

In Britain a colony needs 15 to 20 kg of stored honey to survive the winter. Beekeepers judge what a hive holds by hefting it, lifting one side a few inches, and feed a light one sugar syrup in autumn (Gill, 2021). A crowded colony swarms: half or more of its workers leave with the old queen, and the colony splits in two (Ellis, DeBerry and Crowley).

What each type answers

System context map

For question 1, the boundary is Ana’s hives, with three parties outside it and one exchange each way with each. Nothing inside the hives is drawn, and no amount or date. The marks are chapter 2’s.

Influence map

For question 2, spring weather, flowers within reach and mites per hundred bees bear on honey harvested in a year, weighted by Ana, with no direction: she has no record of which way each acts. Its causal claims are the three effects Ana measured from past years’ records. No amount is drawn. The marks are chapter 3’s.

Causal loop diagram

For question 3, R1, colony growth, runs through foragers, honey and brood, and B1, swarming, through crowding. The loops share only bees in the colony: the more bees, the more crowding, and a crowded colony swarms through B1. Nothing shows what accumulates, nor how many bees crowd a hive. The marks are chapter 4’s, with chapter 5’s.

Stock & flow diagram

For question 4, bees in the colony and honey in the hive accumulate, in bees and kilograms, filled and drained by flows per week. Honey taken drains the stock that honey eaten drains all winter: the stock equation, change in honey in the hive = honey made − honey eaten − honey taken, shows that what Ana takes in late summer has to leave 15 to 20 kg behind. Why the flows change is drawn only as far as three signals. The marks are chapter 6’s, with chapter 7’s.

Feedback control diagram

For question 5, this is the stock & flow diagram’s honey with four variables and an inflow, syrup stored, added, and roles written above names, as chapter 8’s thermostat is drawn over a stock: honey for winter is the target, weight felt when hefting the measured value, honey short of the target the gap, syrup fed per week the corrective action, and honey in the hive the controlled variable. B1, feeding when light, is its control loop. Honey made and honey taken, off the loop, are left out. The marks are chapter 8’s, with chapter 9’s.

Check your understandingA family of five fills its laundry basket in a day or two. Each evening one parent looks in, and runs a wash if the clothes are above a line marked inside the basket; the machine washes at most one basketful a day. The parents' question: does one look each evening keep the basket from overflowing? Which diagram answers it?

A feedback control diagram

Yes. The marked line is a target the parents chose, the evening look a measured value, the clothes above the line a gap, the washes run a corrective action, and the clothes in the basket the controlled variable: a stock with roles written above its names. Whether the washing keeps up turns on the reading once a day and the one basketful a day at most.

A stock & flow diagram

Not quite. The clothes in the basket are a stock, filled as clothes are worn and drained by washes, so this diagram holds half the answer. The marked line and the evening look are a target and a measured value; written above its names as roles, they make it a feedback control diagram.

A causal loop diagram

Not quite. It would show the loop, more clothes in the basket, more washes, fewer clothes, but not that the clothes accumulate, nor the line the parents chose to keep them under.

A system context map

Not quite. It would show the household's boundary and what passes across it, such as clothes bought and given away, and nothing inside it, where the basket is.

System archetype

For question 6, this is the causal loop diagram with one line written on it: Archetype: limits to growth. A reinforcing loop and a balancing loop sharing one variable, bees in the colony, match limits to growth: growth that meets a limit. No role is written, since limits to growth has none. The match is a hypothesis about the loops, not a verdict on the hives. The marks are chapter 10’s, with chapter 11’s.

Converting between types

An influence map into a causal loop diagram, in the lab: chapter 3’s conversion carries over the variables and causal claims only. From Ana’s map, three causal claims carry over, bees in the colony → honey harvested in a year → honey left for winter → bees in the colony, with one −: declared, their path is a balancing loop, taking too much. Ana decides which influence claim she upgrades next, and on what evidence.

A causal loop diagram into a system archetype, in the lab: a causal loop diagram’s file opens in an archetype lab as its own, every variable, effect and loop carried over, with its matches listed. Whoever draws it writes the roles and the declaration.

Check your understandingA causal loop diagram of a town's night buses shows R1, riders → fares collected → buses running → riders, all +, and B1, riders → standing passengers +, standing passengers → riders −. It is opened in an archetype lab and declared limits to growth. What changes in the drawing?

One line is added: Archetype: limits to growth

Yes. The diagram opens with every variable, effect and loop as drawn. A reinforcing loop and a balancing loop sharing riders match limits to growth, and the declaration is the one line added. Limits to growth has no symptomatic solution, fundamental solution or side effect, so no role is written.

The variables are redrawn as stocks and flows

Not quite. That conversion is into a stock & flow diagram, by hand, and no archetype is declared on one. In an archetype lab the causal loop diagram's marks stay as they are.

Roles are written above riders, fares collected and standing passengers

Not quite. Roles are written only where an archetype has them: symptomatic solution, fundamental solution and side effect. Limits to growth has none, so the declaration is the only line added.

Nothing: the match is listed, so no declaration is written

Not quite. The matches are listed after every change, but a declaration is written by whoever draws the diagram: a hypothesis about its loops, checked against the matches.

A causal loop diagram into a stock & flow diagram, by hand: Ana decides what accumulates. Bees in the colony and honey in the hive become stocks; brood raised and swarming become the flows bees emerging and bees leaving in swarms; foragers and crowding fold into the signals that set those flows. The lab has no such conversion: what accumulates is a judgment, and most causal loop diagrams have effects ending at variables that would become stocks, where a stock & flow diagram has no signal end.

A stock & flow diagram into a feedback control diagram, by hand: the stocks, flows, clouds and signals carry over, and Ana decides which variables are the target, the measured value, the gap, the corrective action and the controlled variable, adding those not yet drawn, as the thermostat is drawn over its stock in chapter 8. Auxiliaries become plain variables. Here Ana keeps the honey and honey eaten, and adds the target, the hefted weight, the gap, the syrup fed and syrup stored.

When not to draw

A sentence, a list or a table holds everything a diagram would when the answer is one quantity reached by arithmetic, when nothing comes back around, when no boundary is in dispute, or when the parties can be listed without what passes each way. Each type’s own case is in its first chapter’s What stays informal: chapter 2, chapter 3, chapter 4, chapter 6, chapter 8 and chapter 10.

A diagram shows in one place what is used together, so less has to be searched for; drawn without that grouping, a diagram takes as much searching as the words (Larkin and Simon, 1987).

The bad diagram

What’s wrong with this diagram of a holiday fund?

Nothing in its marks: each of the lab’s checks on a stock & flow diagram passes or is pending.

The sentence

At €50 a week from the €400 already saved, the fund reaches the holiday’s €1,200 in 16 weeks.

The diagram holds one stock, one steady inflow, no outflow and no loop, and the sentence holds all of it, with the numbers missing from the diagram.

Notation moves

Notation move	When	What it shows	Example
Draw a system context map	The question is whom a system deals with	The boundary, the parties outside, what passes each way	Ana’s hives and the bee inspector

Draw an influence map	Many things bear on one outcome, most in unmeasured directions	What bears on the outcome, ranked	honey harvested in a year

Draw a causal loop diagram	A change comes back around	Loops and their kinds	B1 swarming

Draw a stock & flow diagram	Something accumulates	Stocks, the flows that fill and drain them, units	honey in the hive, in kg

Draw a feedback control diagram	Someone holds a quantity near a value they chose	The control loop, its roles written	honey for winter, the target

Draw a system archetype	The loops have a structure that recurs across situations	A hypothesis about the loops	Archetype: limits to growth

Convert an influence map into a causal loop diagram	Causal claims close a path	The loop, to declare	B1 taking too much

Open a causal loop diagram in an archetype lab	The question turns to which archetype the loops match	The loops, their matches listed	the hives’ R1 and B1

Write a sentence	The answer is one quantity reached by arithmetic	Everything the diagram would	the holiday fund

Common misreading

A type is read as a property of the situation: the hives as a stock & flow situation, the holiday fund as a stock & flow problem. The type belongs to the question. Ana’s hives are drawn as all six types, one per question, and the holiday fund’s one question as none.

The strongest objection

The question rarely comes first: people draw to find out what it is. In soft systems methodology the problem in many situations is “what is the problem?”, and a rich picture of the situation is drawn before any problem is defined (Institute for Manufacturing).

Two of the six types are drawn before the question is settled. A system context map holds only a boundary, the parties outside it and what passes each way, and an influence map only an outcome and what bears on it, no direction known. When the question changes, the drawing is converted, as Ana’s influence map was into a causal loop diagram, or redrawn in the type of the new question.

Other families

A line with an arrowhead means changes in four of the six types, passes in a system context map and bears on in an influence map, but then in a process map, where a closed path is rework, not a loop, so a process map can’t share their editor or checker.

Type	Family	Question it answers	A line with an arrowhead means
process map	processes & experience	What steps does the work go through, with its decisions, exceptions and rework?	then: the next step

swimlane diagram	processes & experience	Who does each step, and where does work change hands?	then, across lanes at a change of hands

BPMN	processes & experience	What happens, precisely enough that it could be run?	then; between participants, what is sent

value stream map	processes & experience	Where does material wait from order to delivery, and what starts each step?	then; separate lines carry information

service blueprint	processes & experience	How does what the customer sees connect to the work behind it?	depends on, across the rows; time is position

customer journey map	processes & experience	How does the customer’s experience change, stage by stage?	No arrowheads: stages are columns

theory of change	strategy & decisions	What must change, and in what order, to reach a long-term outcome?	must come before: a precondition

decision tree	strategy & decisions	Which choice, given the chances of what follows each?	No arrowheads: a branch per choice or outcome

stakeholder map	strategy & decisions	Who can affect or is affected by a decision, with what power and interest?	Nothing: each party has a place on two axes

capability map	strategy & decisions	What must an organization be able to do, whatever its structure?	Nothing: a box inside another is part of it

risk bow-tie	strategy & decisions	What could release one hazard, what follows, and what barriers stand between?	No arrowheads: can lead to, threat to top event to consequence

Wardley map	strategy & decisions	What does someone need, what chain of components meets it, and how evolved is each?	moves to: expected evolution; plain lines, needs

Check your understanding

Check your understandingA chess club's treasurer is asked three things. Which one can the treasurer answer without a diagram?

How many weeks until the club's fund, €200 now and €40 added a week, reaches the €680 that new clocks cost

Yes. The answer is one quantity reached by arithmetic, (680 − 200) ÷ 40 = 12 weeks, and a sentence carries it. Nothing comes back around, and no boundary is in question.

Why more members bring more volunteers to teach beginners, and more teaching brings more members

Not quite. That change comes back around, from members to volunteers to members: a loop, which a causal loop diagram shows with its kind.

Whom the club deals with, from the hall it rents to the league it plays in, and what passes each way

Not quite. Several parties, each with something passing each way, are what a system context map shows. A list would name the parties and leave out what passes.

Popular support in Afghanistan, redrawn

Redrawn from PA Consulting Group, “Afghanistan Stability / COIN Dynamics”, in Dynamic Planning for COIN in Afghanistan, working draft (2009), as published by NBC News, page 22, its popular support cluster. © PA Knowledge Limited 2009; its structure and short labels only.

Seven of its 110 or so variables, its popular support cluster, with the lines into it from other clusters left out; its five stocks of people renamed shorter, the first losing & SF, and given units, people, and the month declared as the time unit the slide leaves out; each flow, drawn there running both ways, drawn one way, toward the government’s side, as the net movement, and named; its other two names shortened; its lines left without + or −, as drawn; its double strokes for a significant delay drawn as delays; its color left out.

Question 1 of 3Which question does this part of the slide, drawn as a stock & flow diagram, answer?

Why people move toward the government or toward the insurgents.

Not quite. One auxiliary sets every flow, attractiveness of the government’s path, after a delay. What makes that path attractive is drawn in the slide’s other clusters, about a hundred variables left out here.

How many people hold each of five stances, and how fast they move between neighboring stances.

Yes. Five stocks of people, filled and drained by four flows, each from one stance to the next: what accumulates, and how fast it changes. No one moves from active insurgent supporter to government sympathizer without passing through the fence.

Whether the coalition’s actions shift popular support.

Not quite. No loop closes in the part: no stock reaches attractiveness of the government’s path, so no change in support comes back around to the flows. Any action reaches the flows through the slide’s other clusters, not drawn here.

Question 2 of 3The slide comes from a brief for planning a counterinsurgency: which actions shift popular support toward the government, and how fast. Which drawing would answer that?

The whole slide, since every variable is on it.

Not quite. About 110 variables and the lines among them are on it, and no path through them can be followed by eye, so it answers no question by itself. The brief’s own pages take it a cluster at a time, then one loop at a time.

An influence map, with popular support as its central outcome.

Not quite. An influence map answers what bears on one outcome before anyone knows which way each acts, and the slide’s lines carry no + or −, as a map’s influence claims don’t. But an influence map has no stock or flow, so it can’t show how many people move, or how fast.

A stock & flow diagram of the five stocks with the few loops through their flows that the plan acts on.

Yes. Support accumulates in stocks of people, and an action shifts it by changing how fast people move, through loops that close back on the flows: chapter 7’s stocks inside feedback. Drawn a few loops at a time, each can be followed.

Question 3 of 3Would a sentence do in place of this part?

No: five stocks are too many for a sentence.

Not quite. A sentence holds the five in order. What a sentence can’t hold is a change coming back around through several variables, and in this part none does.

No: a sentence can't carry the delays.

Not quite. A sentence carries a delay in words, after a delay, as a behavior note does; the mark adds nothing a reader of the sentence lacks.

Yes: no loop closes in it, and one sentence holds what it shows.

Yes. People move one stance at a time between active government supporter and active insurgent supporter, toward the government’s side as its path grows more attractive, after a delay, and relative support is read from the four stocks off the fence. Nothing comes back around. Joined to the slide’s loops, the part would have to be drawn again.

Exercises

Passing the checks means meeting the brief, not being right.

CD 01A mountain rescue team

Reasoning2 of 5
Polish2 of 5

Ines is the new leader of a volunteer mountain rescue team in a valley of hill farms. The police take each emergency call from the hills and pass the team a callout, and after each rescue the team sends the police a rescue report. The team carries casualties down to the hospital in the valley town, and the hospital returns the team's stretchers. For a serious injury or a long carry, the team requests a helicopter from the helicopter service, which airlifts the casualty. Donors give the team money, and the team sends them a yearly account of what it spent. Walkers and farmers phone in reports of washed-out paths and fallen bridges, and the team posts route warnings at the valley's car parks. Ines's question: whom does the team deal with, and what passes each way?

Which diagram?What does Ines draw, or write, to answer her question?Pick one to open the brief, the palette and the lab.

A system context map

Yes. Whom the team deals with is the parties outside one boundary, the team's, and what passes each way is the exchanges, each a named one-way line between a party and the boundary. Callouts from the police and rescue reports to them are two exchanges, one each way.

No diagram: a list

Not quite. A list names the five parties but not what passes each way: the police, on a list, carry neither the callouts they send nor the rescue reports they receive.

A causal loop diagram

Not quite. A causal loop diagram shows how a change in one variable produces a change in another, and where those changes come back around in loops. Ines is after who sends what to whom, not what changes what.

An influence map

Not quite. An influence map shows what bears on one outcome, ranked. Ines names no outcome: she is after the parties and what passes between them and the team.

A stock & flow diagram

Not quite. A stock & flow diagram shows what accumulates and what fills and drains it: money in the team's account, filled by donations. The police, the hospital and the walkers have no place in it.

The parties outside one boundary, and what passes each way

The brief

Draw one boundary around the team. checked by the lab
Place at least four external entities outside it. checked by the lab
Draw at least six exchanges, each naming one thing. checked by the lab
Show at least three external entities that both give to the team and receive from it. checked by the lab
The helicopter service is a party outside the team, not part of it. you check this

Your palette

boundary
external entity
exchange

To draw in the lab, use a tablet or a larger screen. Everything else reads normally here.

Drag an external entity to move it. Select an external entity, an exchange or a boundary to change it. Pressing an empty spot adds nothing. Drag a boundary by its outline or its name to move it, and by the square at its corner to resize it. Double-click or double-tap a boundary's name, an external entity or an exchange's name to edit its words in place, or select it and use Rename or the fields under the canvas.

Nothing selected. Select a boundary, an external entity or an exchange on the canvas, and what you can change shows here.

The tools

Arrange V: move an external entity or a boundary (drag it), rename it (double-click it, or Rename or the Name field under the canvas), or select anything.
Boundary B: drag out a boundary around the system, and name it.
External entities T: add an external entity (press an empty spot outside the boundary) and name it.
Exchanges X: draw an exchange by dragging from an external entity into a boundary, or from a boundary out to an external entity, and name it.

Keys

R reverse the selected exchange
Delete delete what's selected
Ctrl+Z undo
Ctrl+Shift+Z redo
Esc clear the selection
Enter finish the words you're writing
Esc cancel them

Keys act on the lab you last used, or on the open lab view, and never while you type.

0 of 9 checks passed; 9 pending.

Draw one boundary around the team. (Not started)No boundary yet. Brief: exactly 1.
Place at least four external entities outside it. (Not started)No external entities yet. Brief: at least 4.
Draw at least six exchanges, each naming one thing. (Not started)No exchanges yet. Brief: at least 6.
Show at least three external entities that both give to the team and receive from it. (Not started)No exchanges yet. Brief: at least 3 external entities that give to the system and receive from it.
The helicopter service is a party outside the team, not part of it. You check this.

Always checked

One outermost boundary: the system (Not started)No boundary drawn yet.
Boundaries nest or stay apart (Not started)No boundary drawn yet.
External entities sit outside every boundary (Not started)No external entity drawn yet.
Every external entity has an exchange (Not started)No exchange drawn yet.
Every exchange has a name (Not started)No exchange drawn yet.

Written feedback

Turn on written feedback

Export

One defensible answer

It opens here once you've drawn a boundary or an external entity in the lab above. Your attempt saves as you draw.

CD 02Moving to another city for a job

Reasoning2 of 5
Polish3 of 5

Mateus has been offered a job in a city four hours away by train, at a salary a third above what he earns now, leading a team of eight people; he has never led a team. His partner, Ilse, teaches piano to thirty pupils near their flat, and her chances of work in the city depend on its music schools, one of which is hiring. His parents live ten minutes away, and he spends about five hours a week helping them, how many depending on his father's health. Only the salary's pull is plain to him: the higher the salary on offer, the stronger his wish to move. Of the rest, he can't yet say which way each pushes: he would miss the Saturdays with his parents and would also have them to himself; leading eight people might draw him to the job or put him off it; and Ilse hasn't said whether starting again in the city would suit her. Mateus's question: what bears on his wish to move?

Which diagram?What does Mateus draw, or write, to answer his question?Pick one to open the brief, the palette and the lab.

A causal loop diagram

Not quite. A causal loop diagram gives every effect a + or − and shows the loops they close. Mateus can give a + or − only to the salary's effect: drawn there, the other effects would carry guesses as findings, and no loop runs through his wish to move.

No diagram: a list

Not quite. A list names the salary, Ilse's chances, the hours with his parents and the team he would lead, but not that the music schools reach his wish to move only through Ilse's chances, or his father's health only through the hours he helps.

An influence map

Yes. What bears on his wish to move is one central outcome and the variables that act on it. That he can't yet say which way most of them push makes each an influence claim, with no + or −; the salary's claim alone is upgraded, with a +.

A system context map

Not quite. A system context map shows the parties outside a boundary and what passes each way: Mateus's household, his parents, the new employer. Who sends what to whom leaves out what draws him to the city and what holds him at home.

A stock & flow diagram

Not quite. A stock & flow diagram shows what accumulates and what fills and drains it: Mateus's savings, filled faster by the higher salary. His question is what bears on one wish, and a wish fills from no flow.

What bears on one outcome, most of it in no known direction

The brief

Draw at least four direct influences on Mateus's wish to move. checked by the lab
Draw at least one indirect influence. checked by the lab
Leave at least three claims without a + or −. checked by the lab
Upgrade exactly one claim: the one whose direction Mateus can say. checked by the lab
Each variable is a quantity that could be more or less, such as hours a week helping his parents, not a topic such as family. you check this

Your palette

variable
polarity
influence claim
central outcome

To draw in the lab, use a tablet or a larger screen. Everything else reads normally here.

Press an empty spot to add a variable and type its name. Drag a variable to move it. Select a variable or an influence claim to change it. Double-click or double-tap a variable to edit its words in place, or select it and use Rename or the fields under the canvas.

Nothing selected. Select a variable or an influence claim on the canvas, and what you can change shows here.

The tools

Variables V: add a variable (press an empty spot), move one (drag it), rename one (double-click it, or Rename under the canvas), or select anything.
Influence claims E: draw an influence claim by dragging from one variable to another.

Keys

R reverse the selected claim
O mark the selected variable as the central outcome, or take the mark off
+− upgrade the selected influence claim to a causal claim; the same key again makes it an influence claim again
Delete delete what's selected
Ctrl+Z undo
Ctrl+Shift+Z redo
Esc clear the selection
Enter finish the words you're writing
Esc cancel them

Keys act on the lab you last used, or on the open lab view, and never while you type.

0 of 7 checks passed; 7 pending.

Draw at least four direct influences on Mateus's wish to move. (Not started)No claims yet. Brief: at least 4 direct influences.
Draw at least one indirect influence. (Not started)No claims yet. Brief: at least 1 indirect influence.
Leave at least three claims without a + or −. (Not started)No claims yet. Brief: at least 3 influence claims.
Upgrade exactly one claim: the one whose direction Mateus can say. (Not started)No claims yet. Brief: exactly 1 causal claim.
Each variable is a quantity that could be more or less, such as hours a week helping his parents, not a topic such as family. You check this.

Always checked

One central outcome (Not started)No variable drawn yet.
Every variable has a path of claims to the central outcome (Not started)No claims yet.
No variable's name breaks the more test's three rules (Not started)No variable drawn yet.

Written feedback

Turn on written feedback

Export

One defensible answer

It opens here once you've drawn at least one variable in the lab above. Your attempt saves as you draw.

CD 03Carbon dioxide in the atmosphere

Reasoning3 of 5
Polish3 of 5

Halima reads that the world's yearly emissions of carbon dioxide may soon stop growing. Burning fossil fuels and clearing land put about 11 billion tonnes of carbon a year into the air, as carbon dioxide. The oceans absorb about 3 billion tonnes of it a year, and forests and other vegetation on land about 2; the rest stays in the air. Suppose emissions hold steady at 11 billion tonnes a year from now on, and the oceans and the vegetation go on absorbing about as much as now. Count the carbon dioxide by the carbon it holds, in billion tonnes, and time in years. Halima's question: if emissions stop growing and hold steady, does the carbon dioxide in the air stop rising?

Which diagram?What does Halima draw, or write, to answer her question?Pick one to open the brief, the palette and the lab.

A causal loop diagram

Not quite. A causal loop diagram shows that more emissions bring more carbon dioxide in the air, a + effect, but not that the carbon dioxide accumulates. Read as an effect, steady emissions give steady carbon dioxide, which is wrong here.

A stock & flow diagram

Yes. Whether the carbon dioxide in the air stops rising is a question about how an amount changes over time: it is a stock, filled by emissions and drained by what the oceans and vegetation on land absorb. Holding emissions steady fixes the inflow, not the stock: with about 11 in and about 5 out each year, the stock goes on rising.

No diagram: a sentence

Not quite. The sentence is what Halima writes once the stock is drawn: while emissions exceed what the oceans and vegetation on land absorb, the carbon dioxide in the air rises. Without the stock, most adults Sterman and Booth Sweeney tested expected it to hold steady once emissions did.

An influence map

Not quite. An influence map shows what bears on one outcome, ranked. What bears on the carbon dioxide in the air is known here: emissions and what is absorbed. Halima's question is how much of it there is as the years pass.

A feedback control diagram

Not quite. A feedback control diagram shows a target, a measured value and a correction that closes the gap between them. Nothing here holds the carbon dioxide in the air to a target; Halima's question is what steady emissions do to it.

An amount filled faster than it drains

The brief

Draw the carbon dioxide in the air as one stock, counted in billion tonnes of carbon. checked by the lab
Draw the emissions as an inflow. checked by the lab
Draw at least one outflow: what the oceans and vegetation on land absorb. checked by the lab
Add a behavior-over-time graph of the stock while emissions hold steady: its direction is Halima's answer. checked by the lab
Emissions held steady still exceed what the oceans and vegetation on land absorb. you check this

Your palette

stock
flow
cloud
behavior-over-time graph

To draw in the lab, use a tablet or a larger screen. Everything else reads normally here.

Drag a stock, a cloud or a graph to move it. Select a stock, a flow, a cloud or a graph to change it. Pressing an empty spot adds nothing. Double-click or double-tap a stock's name or units or a flow's name to edit its words in place, or select it and use Rename or the fields under the canvas.

Nothing selected. Select a stock, a flow, a cloud or a behavior-over-time graph on the canvas, and what you can change shows here.

The tools

Arrange V: move a stock, a cloud or a graph (drag it), rename a stock (double-click it, or Rename under the canvas), or select anything.
Stocks S: add a stock (press an empty spot) and name it.
Flows M: draw a flow by dragging from a stock or an empty spot to a stock or an empty spot, and name it; clouds appear at empty ends.
Behavior-over-time graphs H: select a stock, an auxiliary or a flow, then press an empty spot, to add its behavior-over-time graph there.

Keys

R reverse the selected flow
Delete delete what's selected
Ctrl+Z undo
Ctrl+Shift+Z redo
Esc clear the selection
Enter finish the words you're writing
Esc cancel them

Keys act on the lab you last used, or on the open lab view, and never while you type.

0 of 9 checks passed; 9 pending.

Draw the carbon dioxide in the air as one stock, counted in billion tonnes of carbon. (Not started)No stocks yet. Brief: exactly 1.
Draw the emissions as an inflow. (Not started)No flows yet. Brief: at least 1 inflow.
Draw at least one outflow: what the oceans and vegetation on land absorb. (Not started)No flows yet. Brief: at least 1 outflow.
Add a behavior-over-time graph of the stock while emissions hold steady: its direction is Halima's answer. (Not started)No behavior-over-time graph yet. Brief: a behavior-over-time graph of a stock that rises.
Emissions held steady still exceed what the oceans and vegetation on land absorb. You check this.

Always checked

Every stock has units (Not started)No stock drawn yet.
The time unit is given (Not started)No flow drawn yet.
Every stock has a flow in or out (Not started)No stock drawn yet.
Every flow has a name (Not started)No flow drawn yet.
No variable's name breaks the more test's three rules (Not started)No variable drawn yet.

Written feedback

Turn on written feedback

Export

One defensible answer

It opens here once you've drawn at least one stock in the lab above. Your attempt saves as you draw.

CD 04Two siblings and one games console

Reasoning3 of 5
Polish3 of 5

Noor, eleven, and Felix, nine, share one games console. Each Sunday their father splits the coming week's turns on it between them by their best scores that week in the racing game they both play: the higher Noor's best score, the larger her share of the turns, and the higher Felix's, the smaller her share. The more turns a child gets, the more hours that child plays, and the more hours played, the higher that child's best score. In the first week, Noor scored a few points higher than Felix. Their father's question: is this a story others have seen, and how does it usually run?

Which diagram?What does their father draw, or write, to answer his question?Pick one to open the brief, the palette and the lab.

A causal loop diagram

Not quite. A causal loop diagram shows the two reinforcing loops through Noor's share of the turns, and no archetype. The same loops drawn there and opened in an archetype lab, with the archetype they match declared, are the diagram that answers whether others have seen this story.

An influence map

Not quite. An influence map shows what bears on one outcome, its directions left open until measured. The father's rule fixes every direction here, and the effects close two loops, which no one declares on an influence map.

A system archetype

Yes. The father asks after a recurring loop structure with a name: a story others have seen, and how it usually runs. The two reinforcing loops, one through each child's hours, share Noor's share of the turns, and that structure matches an archetype, declared in one line; how the split usually runs is that archetype's known course.

A stock & flow diagram

Not quite. A stock & flow diagram shows what accumulates and what fills it, such as each child's hours played. The father's question is whether the two loops through the split are a story with a name, which no stock or flow carries.

No diagram: a sentence

Not quite. A sentence states the father's rule and Noor's lead in the first week. Whether the story recurs elsewhere is read from its loops: two reinforcing loops through one split, matched to an archetype.

Two loops through one split, and the name of their story

The brief

Draw two reinforcing loops, one through each child's hours on the console. checked by the lab
Match the two loops to one of chapter 10's archetypes. checked by the lab
Declare that archetype in one line. checked by the lab
Add a behavior note on how the split runs, week by week. checked by the lab
The father's rule is one variable, Noor's share of the turns, on both loops. you check this
In the note: Noor's lead of a few points in the first week, and her share larger every week after. you check this

Your palette

variable
effect
polarity
loop
reinforcing loop
behavior note
archetype

To draw in the lab, use a tablet or a larger screen. Everything else reads normally here.

Press an empty spot to add a variable and type its name. Drag a variable to move it. Select a variable, an effect or a loop label to change it. Drag a behavior note to move it. Double-click or double-tap a variable, a loop's label or name or a behavior note to edit its words in place, or select it and use Rename or the fields under the canvas.

Nothing selected. Select a variable, an effect, a loop label, a behavior note or a declared archetype on the canvas, and what you can change shows here.

The tools

Variables V: add a variable (press an empty spot), move one (drag it), rename one (double-click it, or Rename under the canvas), or select anything.
Effects E: draw an effect by dragging from one variable to another.
Loop L: declare a loop by selecting its effects in order, then label and name it.
Note N: place a behavior note (press where it goes).
Archetype K: declare an archetype: press an empty spot, then choose which of the nine.

Keys

R reverse the selected effect
+− the selected effect's polarity
Delete delete what's selected
Ctrl+Z undo
Ctrl+Shift+Z redo
Esc clear the selection
Enter finish the words you're writing
Esc cancel them

Keys act on the lab you last used, or on the open lab view, and never while you type.

Archetypes the structure matches

Read from the loops and their kinds as drawn, after each change. Nothing here is saved.

No archetype matches yet.

0 of 9 checks passed; 9 pending.

Draw two reinforcing loops, one through each child's hours on the console. (Not started)No loop declared yet. Brief: exactly 2 reinforcing loops.
Match the two loops to one of chapter 10's archetypes. (Not started)No effect has a polarity yet. Brief: success to the successful.
Declare that archetype in one line. (Not started)No variables yet. Brief: exactly 1 declared archetype.
Add a behavior note on how the split runs, week by week. (Not started)No loop declared yet. Once one is, add a behavior note naming what it predicts.
The father's rule is one variable, Noor's share of the turns, on both loops. You check this.
In the note: Noor's lead of a few points in the first week, and her share larger every week after. You check this.

Always checked

Each loop's kind matches its − effects (Not started)No loop declared yet.
Loop labels are unique and match their kind (Not started)No loop declared yet.
Every effect has a polarity (Not started)No effects yet.
The structure matches each declared archetype (Not started)No archetype declared yet.
No variable's name breaks the more test's three rules (Not started)No variable drawn yet.

Written feedback

Turn on written feedback

Export

One defensible answer

It opens here once you've drawn at least one variable in the lab above. Your attempt saves as you draw.

CD 05A canal through a dry summer

Reasoning4 of 5
Polish4 of 5

Through a dry summer, Ruth keeps the long top stretch of a canal deep enough for boats. Every boat through a lock at either end of the stretch draws thousands of litres of water out of it, and on a busy day dozens of boats pass. Water comes into the stretch from a lake dammed in the hills, along a feeder, and Ruth sets how much she lets in each day; the feeder carries only so much a day. She reads the depth on a gauge board once each morning, and the further it reads below the depth boats need, the more water she lets in that day. Count the water in the stretch as its depth, in centimetres, and time in days. Ruth's question: how do her morning reading and the water she lets in hold the stretch at the depth boats need, and where can that fall short?

Which diagram?What does Ruth draw, or write, to answer her question?Pick one to open the brief, the palette and the lab.

A stock & flow diagram

Not quite. A stock & flow diagram shows the water in the stretch, the water from the hill lake and the water drawn by the locks: the same stock and flows a feedback control diagram of the stretch holds, without its roles. With no target, gap or corrective action written, it shows neither the depth Ruth holds the stretch to nor that her morning reading arrives late.

A causal loop diagram

Not quite. A causal loop diagram shows the balancing loop through the depth and the water let in, but not what accumulates, nor which variable is the target and which the reading. Ruth's question turns on both.

A system context map

Not quite. A system context map shows the parties outside the canal, such as boaters and the lake's owners, and what passes each way. It leaves out how the depth is held, and where that falls short.

A feedback control diagram

Yes. Ruth holds the stretch at the depth boats need: that depth is a target, and her morning reading a measured value, up to a day behind the water in the stretch. The gap between them sets the water she lets in, which the feeder limits: one control loop, its roles written over the stretch's stock and flows.

No diagram: a sentence

Not quite. A sentence states Ruth's rule: the further the depth reads below what boats need, the more water she lets in. Where that falls short, between one morning's reading and the next and at the feeder's limit, shows on the loop drawn with its delay and its limit.

A depth held by a reading once a day and an inflow with a limit

The brief

Draw the water in the stretch as one stock, counted in centimetres of depth. checked by the lab
Close one control loop through the water from the hill lake. checked by the lab
Write one target: the depth boats need. checked by the lab
Draw the boats through the locks as an external driver acting on the water in the stretch. checked by the lab
Mark the once-a-morning reading as a delay on the return path. checked by the lab
Write what the feeder carries in a day as the limit on the water Ruth lets in. checked by the lab
The target depth is Ruth's choice: no signal ends at it. you check this

Your palette

variable
polarity
delay
loop
balancing loop
external driver
gapa role, written above its variable's name
stock
flow
cloud
signal
targeta role, written above its variable's name
corrective actiona role, written above its variable's name
controlled variablea role, written above its variable's name
measured valuea role, written above its variable's name
saturation

To draw in the lab, use a tablet or a larger screen. Everything else reads normally here.

Press an empty spot to add a variable and type its name. Drag a variable to move it. Select a variable, a signal or a loop label to change it. Double-click or double-tap a stock's name or units, a flow's name, a variable or a loop's label or name to edit its words in place, or select it and use Rename or the fields under the canvas.

Nothing selected. Select a stock, a flow, a signal, a cloud, a variable or a loop label on the canvas, and what you can change shows here.

The tools

Variables V: add a variable (press an empty spot), move one (drag it), rename one (double-click it, or Rename under the canvas), or select anything.
Stocks S: add a stock (press an empty spot) and name it.
Flows M: draw a flow by dragging from a stock or an empty spot to a stock or an empty spot, and name it; clouds appear at empty ends.
Signals E: draw a signal by dragging from a variable, a stock or a flow's valve to a variable or a flow's valve.
Loop L: declare a loop by selecting its signals and flows in order, then label and name it.

Keys

R reverse the selected signal or flow
P the selected variable's role, in turn: none, then each role this exercise offers
+− the selected signal's polarity
Delete delete what's selected
Ctrl+Z undo
Ctrl+Shift+Z redo
Esc clear the selection
Enter finish the words you're writing
Esc cancel them

Keys act on the lab you last used, or on the open lab view, and never while you type.

0 of 18 checks passed; 18 pending.

Draw the water in the stretch as one stock, counted in centimetres of depth. (Not started)No stocks yet. Brief: exactly 1.
Close one control loop through the water from the hill lake. (Not started)No loop declared yet. Brief: exactly 1 control loop.
Write one target: the depth boats need. (Not started)No variables yet. Brief: exactly 1 target.
Draw the boats through the locks as an external driver acting on the water in the stretch. (Not started)No external driver yet. Brief: at least 1 external driver acting on a controlled variable.
Mark the once-a-morning reading as a delay on the return path. (Not started)No control loop yet. Brief: at least 1 delay on a return path.
Write what the feeder carries in a day as the limit on the water Ruth lets in. (Not started)No corrective action yet. Brief: at least 1 corrective action with a saturation.
The target depth is Ruth's choice: no signal ends at it. You check this.

Always checked

Each loop's kind matches its − effects (Not started)No loop declared yet.
Loop labels are unique and match their kind (Not started)No loop declared yet.
No effect runs into an external driver (Not started)No variable is marked as an external driver yet.
Every stock has units (Not started)No stock drawn yet.
The time unit is given (Not started)No flow drawn yet.
Every stock has a flow in or out (Not started)No stock drawn yet.
Every flow has a name (Not started)No flow drawn yet.
Each gap reads a target and a measured value, with opposite polarities (Not started)No gap yet.
Each measured value reads a controlled variable (Not started)No measured value yet.
Each gap closes a balancing loop (Not started)No gap yet.
No external driver acts on a gap or a target (Not started)No variable is marked as an external driver yet.
No variable's name breaks the more test's three rules (Not started)No variable drawn yet.

Written feedback

Turn on written feedback

Export

One defensible answer

It opens here once you've drawn at least one variable in the lab above. Your attempt saves as you draw.

CS 12Kelsham Primary School: the council's question

Reasoning4 of 5
Polish4 of 5

In October 2026 Kelsham Primary School has 88 pupils, and the county council asks whether to close it. David Brennan, its officer for school places, has the births in the villages to 2025: 12 in 2023, 12 in 2024 and 11 in 2025. Each year's children start school in the September four years later, fewer of them at Kelsham than were born, since some families choose Brayford Primary School: in the year to October 2026, 9 children started and 16 pupils left. Larkfield Homes will finish the 60 homes at Mill Lane from 2027 to 2029, and the county council counts 0.25 children of primary school age for each new home: 15 children in all, joining as the homes are first lived in, and none once the last one is. Tom Hale tells the council the homes will turn the roll around. Count the pupils in pupils, and time in years. David Brennan's question: once the last Mill Lane home is lived in, does the roll go on falling?

Which diagram?What does David Brennan draw, or write, to answer his question?Pick one to open the brief, the palette and the lab.

A causal loop diagram

Not quite. In a causal loop diagram, homes lived in at Mill Lane → pupils on roll is a + effect, which reads as more homes, more pupils for good. The homes bring their 15 children once, as they are first lived in; whether the roll goes on falling afterwards turns on what fills it and what drains it each year.

A stock & flow diagram

Yes. Whether the roll goes on falling is a question about how an amount changes over the years: the pupils on roll are a stock, filled by the children starting and the children moving into Mill Lane, and drained by the pupils leaving. The inflow from Mill Lane stops once the last home is lived in, and the children starting, fewer than the births four years before, are fewer each year than the pupils leaving.

An influence map

Not quite. An influence map shows what bears on one outcome, ranked, its directions left open. Here every direction is known: the births, the homes and the pupils leaving each fill or drain the roll. David Brennan's question is how many pupils are left as the years pass.

A feedback control diagram

Not quite. A feedback control diagram shows a target, a measured value and a correction that closes the gap between them. Nothing here holds the roll to a target; the question is where the roll goes once the homes are lived in.

No diagram: a sentence

Not quite. The sentence is what David Brennan writes once the roll is drawn as a stock: after 2029 only the children starting fill it, and fewer start than leave each year, so it goes on falling. Without the stock, Tom Hale's reading, that the homes turn the roll around, goes unchecked.

Choosing the drawing for whether the roll recovers

The brief

Draw the pupils on roll as one stock, counted in pupils. checked by the lab
Draw two inflows: the children starting each September, and the children moving into the Mill Lane homes. checked by the lab
Draw the pupils leaving as one outflow. checked by the lab
Show the stock equation. checked by the lab
Draw the births in the villages with a signal to the children starting, delayed by the four years before a child starts. checked by the lab
Add a behavior-over-time graph of the roll once the last Mill Lane home is lived in: its direction is David Brennan's answer. checked by the lab
The inflow from Mill Lane ends with the last home lived in; the children starting go on each September. you check this

Your palette

stock
flow
cloud
auxiliary
signal
stock equation
polarity
delay
behavior-over-time graph

To draw in the lab, use a tablet or a larger screen. Everything else reads normally here.

Press an empty spot to add an auxiliary and type its name. Drag a stock, an auxiliary, a cloud or a graph to move it. Select anything drawn to change it. Double-click or double-tap a stock's name or units, an auxiliary or a flow's name to edit its words in place, or select it and use Rename or the fields under the canvas.

Nothing selected. Select a stock, an auxiliary, a flow, a signal, a cloud or a behavior-over-time graph on the canvas, and what you can change shows here.

The tools

Auxiliaries V: add an auxiliary (press an empty spot), move a stock, an auxiliary, a cloud or a graph (drag it), rename one (double-click it, or Rename under the canvas), or select anything.
Stocks S: add a stock (press an empty spot) and name it.
Flows M: draw a flow by dragging from a stock or an empty spot to a stock or an empty spot, and name it; clouds appear at empty ends.
Signals E: draw a signal by dragging from a stock, an auxiliary or a flow's valve to an auxiliary or a flow's valve.
Behavior-over-time graphs H: select a stock, an auxiliary or a flow, then press an empty spot, to add its behavior-over-time graph there.

Keys

R reverse the selected signal or flow
Q the selected stock's equation, on or off
+− the selected signal's polarity
Delete delete what's selected
Ctrl+Z undo
Ctrl+Shift+Z redo
Esc clear the selection
Enter finish the words you're writing
Esc cancel them

Keys act on the lab you last used, or on the open lab view, and never while you type.

0 of 11 checks passed; 11 pending.

Draw the pupils on roll as one stock, counted in pupils. (Not started)No stocks yet. Brief: exactly 1.
Draw two inflows: the children starting each September, and the children moving into the Mill Lane homes. (Not started)No flows yet. Brief: exactly 2 inflows.
Draw the pupils leaving as one outflow. (Not started)No flows yet. Brief: exactly 1 outflow.
Show the stock equation. (Not started)No stocks yet. Brief: at least 1 stock equation.
Draw the births in the villages with a signal to the children starting, delayed by the four years before a child starts. (Not started)No signals yet. Brief: at least 1 signal delay.
Add a behavior-over-time graph of the roll once the last Mill Lane home is lived in: its direction is David Brennan's answer. (Not started)No behavior-over-time graph yet. Brief: a behavior-over-time graph of a stock that falls.
The inflow from Mill Lane ends with the last home lived in; the children starting go on each September. You check this.

Always checked

Every stock has units (Not started)No stock drawn yet.
The time unit is given (Not started)No flow drawn yet.
Every stock has a flow in or out (Not started)No stock drawn yet.
Every flow has a name (Not started)No flow drawn yet.
No variable's name breaks the more test's three rules (Not started)No variable drawn yet.

Written feedback

Turn on written feedback

Export

One defensible answer

It opens here once you've drawn at least one stock in the lab above. Your attempt saves as you draw.

Sources

Maggie Gill, “To Feed or Not to Feed?”, BBKA News (August 2021): 269–271, on a colony’s winter stores, feeding syrup in autumn, and hefting.
James D. Ellis, Sara DeBerry and John Crowley, “Swarm Control for Managed Beehives”, UF/IFAS Extension, on crowding as a cause of swarming, and the workers who leave with the old queen.
Jill H. Larkin and Herbert A. Simon, “Why a Diagram Is (Sometimes) Worth Ten Thousand Words”, Cognitive Science 11, no. 1 (1987): 65–99, on diagrams that put together what is used together, pp. 98–99.
Institute for Manufacturing, University of Cambridge, “Soft Systems Methodology”, summarizing Checkland and Scholes (1990).
Pierre Friedlingstein and others, “Global Carbon Budget 2024”, Earth System Science Data 17 (2025): 965–1039, for CD 03’s carbon flows.
John D. Sterman and Linda Booth Sweeney, “Understanding Public Complacency About Climate Change: Adults’ Mental Models of Climate Change Violate Conservation of Matter”, Climatic Change 80 (2007): 213–238, for CD 03.
Canal & River Trust, Water management FAQs and Day to day, and the Macclesfield Canal Society, Reservoirs & feeders, for CD 05.