3 · Route
For Both Executive and Technical ReadersRouting is a satisfiability check against Scope Cards, not a guess, not a search, not a recommendation.
01 What happens
A satisfiability check. Three outcomes. No guessing.
Route receives the typed CausalQuery and checks it against every model in the Model Registry. Each model carries a Scope Card, a machine-readable declaration of which variables it covers, which population regime it was elicited for, and which rungs it supports.
A model covers the query when: (1) its variables contain the estimand’s variables, (2) its regime contains the query population, and (3) it supports the requested rung. All three must hold.
02 In / Out
A typed query in. A model set out, or a structured refusal.
IN CausalQuery from Step 2
IN Model Registry (Scope Cards)
OUT RouteResult: single model, composition path, or refusal
| Path | Meaning |
|---|---|
| Single | One model covers the query, sepsis.bayes |
| Composition | No single model covers it, but two together do, sepsis.bayes + icu-risk.bayes |
| Refuse | No model covers it, e.g. "no model covers Readmission in regime=paediatric," stated as a gap, not guessed around |
03 Scope Cards
Every model declares its own boundary. Routing enforces it.
| Model | sepsis.bayes |
| Variables | Sepsis, Lactate, Treatment, Septic Appearance |
| Regime | icu_adult |
| Supported rungs | 1, 2, 3, observational, interventional, counterfactual |
04 Three outcomes
Single model, composition, or named refusal. Nothing else.
Single model: exactly one model covers the query. Proceeds to Step 4.
Composition path: no single model covers but the union of several does. Proceeds to Step 4 then Step 5.
Refusal: no covering model exists. Returns a structured RefusalObject naming the specific gap.
A gap in the Model Registry is information. It tells you exactly what the practice does not yet cover, and what model needs to be built next.
05 Architecture components
Composability owns the registry that Route queries.
Pipeline →, Route is Step 3.
Composability →, defines the Model Registry and Scope Card schema.