# `Statifier.Effect.DatamodelInit`
[🔗](https://github.com/riddler/statifier-ex/blob/v2.0.0/lib/statifier/effect/datamodel_init.ex#L1)

Payload for `{:datamodel_init, %__MODULE__{}}` - the datamodel's starting
map, emitted once per `Statifier.Interpreter.initialize/2`, before the
first `<data>` value is evaluated (plan decision 1).

`datamodel` is `machine_state.datamodel` as it stands after spec 5.3.3's
unconditional `<data>` creation (`Statifier.Interpreter.Datamodel.seed/2`)
and before the binding fold that follows it. That ordering is what makes
this payload carry exactly the three contributions no
`{:datamodel_change, _}` effect can ever describe: `MachineState.new/2`'s
`:datamodel` option, `SystemVariables.initial/2`'s four spec 5.10 system
variables, and the `:undefined` seed (ADR-0037's spelling) for every
declared id. Taking the baseline after binding would restate values the
per-`<data>` binding effects already carry (decision 1).

Emitted unconditionally, once, even for a chart with no `<datamodel>` at
all (decision 2) - the four system variables mean the map is never empty,
so a consumer always has a starting point with nothing to special-case.

Deliberately carries no `binding`, `env_ids`, or declared-id list: those
are facts about the `%Statifier.Machine{}`, and
`docs/observability.md:94-115` constraint 3's model is that tooling
resolves machine facts through the machine, not through an effect payload
(decision 6). What this payload carries instead is *values*, which exist
nowhere else - the environment's `:datamodel` option and the session's
`_sessionid` are not recoverable from the machine alone.

`datamodel` is a term reference, not a deep copy - Elixir maps are
immutable, so this struct costs one word, once per session, not O(datamodel
size). Neither `datamodel` nor the `:undefined` atom inside it commits to a
wire format: `docs/observability.md:173-179` names "no wire format" as an
explicit non-goal for this repo, and per ADR-0025 serialization is
statifier-ui's own half of the mirror.

# `t`

```elixir
@type t() :: %Statifier.Effect.DatamodelInit{
  datamodel: map(),
  macrostep: non_neg_integer(),
  microstep: non_neg_integer(),
  round: non_neg_integer()
}
```

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*Consult [api-reference.md](api-reference.md) for complete listing*