A chart is a picture of an answer. Somebody did the work, reached a conclusion, and drew it. The reader can look at the picture and agree or disagree, and that is the end of the transaction. Suppose the reader wants to know what happens at a different gas price, or under a different recovery rate, or if one assumption turns out to be wrong. The chart has nothing to say, since the assumptions were consumed in making it.
A world model is the thing that was consumed. It is the subject represented as a working system, with the quantities that describe it, the relationships between them, and the rules by which the whole thing moves when any one part changes. The chart is one view of that system. The report is another. The reader who can reach the model can ask questions nobody anticipated.
Serinyx builds one for every report. This note sets out what is inside them, using the three reports we have published as examples.
Entities, state and dynamics
A world model has three parts, and they are worth naming separately because the third one is where most published analysis stops short.
The entities are the things the subject is actually made of. In the hydrogen report they are reactors, methane, electricity, solid carbon, the buyers of that carbon, and the regulator setting the threshold. In the battery-recycling report they are packs, factory scrap, black mass, three refining routes, plants, metal prices and a statutory calendar.
The state is the evidenced quantity attached to each of those things. Not a plausible number, and not a round number chosen because it sits nicely on an axis. Every input in our models carries three things. There is a default, which is the report's own central case. There is a range whose ends are the extremes of published estimates. Finally there is a note recording which published source each end came from. Where a value is an assumption rather than a measurement, it says so in its own first sentence, and it does not get to pretend otherwise.
The dynamics are the rules by which changing one quantity changes the others. This is the part that distinguishes a model from a table. The hydrogen model is the clearest illustration. Moving the carbon price moves the cost of hydrogen, which moves which production routes are viable, which moves the comparison against grey, blue and green supply. The carbon price moves the cost by 5.20 euros a kilogram across its published range. That is more than the gas price, the electricity price, the capacity factor, the cost of capital and the build cost combined. The model computes that ranking from its own equations rather than asserting it, and if you remove the carbon buyer the ranking inverts and the carbon price drops from first place to sixth.
One world, many views
The reason to insist on the word "world" rather than "calculator" is that everything the reader sees has to be a view onto the same underlying state. Not a set of separately wired panels that happen to sit on one page.
That sounds like an aesthetic preference. It is an evidential one. When two parts of a page are wired separately, they can disagree, and a reader has no way to tell which one is right. When they are views of a single state, they cannot disagree, and one input change moves all of them together in the same frame.
We test for this now, because we got it wrong. An early version of one of our models had a belief calculation and an economics calculation that never exchanged a value. Both halves were individually correct, every number in both traced to a source, and the whole thing passed every mechanical check we had. It was still two models in a trench coat, and it was caught only when somebody ran the scenarios and noticed that changing the price path left the conclusion identical to eight decimal places. Every reader-settable input in every model now has to move something outside its own part of the system, and an input that moves nothing is deleted or connected.
What a world model is allowed to look like
For most of this year we forbade ourselves from describing the appearance of these models at all. The specification said what was true and computable, and a separate team decided how to represent it. The rule existed because specifications kept drifting into describing pictures instead of mechanisms, which is an easy failure, since describing a picture is easier than describing a system.
In September we amended it, and the amendment matters. The only constraint on a world model is the report and the evidence in it. How it is represented is not constrained. A model may be specified with geometry, dimensionality, spatial structure, motion, and forms nobody here has built before. It may be volumetric. It may be walkable. It may be scrubbed through time rather than read. It need not resemble a chart, a page, or a document at all.
What the amendment does not touch is the part that keeps it honest. Every quantity still traces to a source. One piece of evidence still grounds one parameter, and may not be quietly reused to support a second thing it never measured. The model must still be able to fail. Freedom of representation is not freedom of assertion. A relationship drawn convincingly in three dimensions that the evidence does not support is worse than the same error drawn flat, precisely because it is more convincing.
What separates a model from a demonstration
Four properties, and each of them is a constraint we accepted because the alternative is a toy.
The default is the report's case, and the reader can always return to it. A model that opens on a flattering configuration is an advertisement.
Ranges come from the published record, not from the interface. The ends of every range are real published extremes. When a reader pushes an input beyond what the evidence supports, the model still computes, and every affected output is marked as standing outside the evidence.
The model can lose. Each one carries pre-registered conditions under which the report's own conclusion holds, strains, or fails. The thresholds are taken from the evidence rather than set by taste. This is the property most easily faked and the one worth checking first. In the hydrogen model, a configuration can be the cheapest option available and still fail the climate test. A methane leak rate above 0.63 per cent invalidates the case, and both published figures fail that threshold. A model in which the conclusion cannot be overturned is not a model of anything.
It refuses. Where the evidence will not support a forecast, the model does not produce one, and it records why. Across the published set, several sub-models are formally refused rather than estimated. Adoption forecasting is refused where the record is a snapshot and not a series. Currency-denominated returns are refused where no exchange rate exists in the source material. Market sizing is refused where three vendor forecasts disagree by a factor of six. An honest refusal is more useful than a confident number, since the reader can see exactly which question is still open.
Where this sits in the series
The three published reports are The Demo Economy, on the gap between announced humanoid-robot adoption and the audited record, Europe's Most Valuable Mine Is a Scrapheap, on the industrial economics of battery recycling, and Hydrogen's Dark Horse Is Turquoise, on methane pyrolysis. Each is built on a model of the kind described here. The series continues, and each new report carries its own.
The models behind the published three run to between roughly fifty and a hundred and twenty evidenced inputs, and between seventy and a hundred and sixty equations. Each equation names the published method it comes from. Every one is checked against test cases that state the inputs and the expected outputs in advance. A built version that drifts from the specification can then be detected rather than argued about.
None of that is the interesting part. The interesting part is what a reader who disagrees with us can do. They can find out precisely what they would have to believe in order to be right, and whether the published record allows them to believe it. That is what we think a research deliverable should do.