# `HL7v2.Validation.Structural`
[🔗](https://github.com/Balneario-de-Cofrentes/hl7v2/blob/v3.10.1/lib/hl7v2/validation/structural.ex#L1)

Positional structural validation against HL7 v2.5.1 abstract message definitions.

Validates segment ordering, group structure, and cardinality by walking the
actual segment stream against the structure AST in order — a state-machine
approach that correctly handles:

- **Segments in multiple groups** — ROL can appear in PATIENT, VISIT,
  PROCEDURE, INSURANCE; each group consumes its own occurrences
- **Repeating groups** — each repetition independently validates required
  children (e.g., ADT_A39 PATIENT group needs PID+MRG per occurrence)
- **Positional ordering** — violations are detected naturally because the
  walk is sequential
- **Cardinality** — non-repeating segments/groups consumed at most once

## Modes

- `:lenient` (default) — unexpected segments are warnings, missing required
  segments are errors
- `:strict` — all structural violations are errors

## Usage

    structure = HL7v2.Standard.MessageStructure.get("ORU_R01")
    segment_ids = ["MSH", "PID", "OBR", "OBX", "NTE"]
    errors = HL7v2.Validation.Structural.validate(structure, segment_ids)

# `error`

```elixir
@type error() :: %{
  level: :error | :warning,
  location: binary(),
  field: atom() | nil,
  message: binary()
}
```

# `validate`

```elixir
@spec validate(HL7v2.Standard.MessageStructure.structure(), [binary()], keyword()) ::
  [error()]
```

Validates a list of segment IDs against a message structure definition.

Returns a list of errors/warnings (empty list = valid).

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