Boxic DMN

Boxic DMN is a native Elixir loader, validator, and evaluator for Decision Model and Notation (DMN) 1.5 models. It uses boxic_feel for expression evaluation and does not require a JVM.

Installation

Add boxic_dmn to mix.exs:

def deps do
  [
    {:boxic_dmn, "~> 0.3.0"}
  ]
end

Quick start

Load XML explicitly, validate its normalized model, and evaluate a decision:

xml = """
<definitions xmlns="https://www.omg.org/spec/DMN/20230324/MODEL/"
  id="example" name="Example" namespace="https://example.com/boxic">
  <decision id="greeting" name="Greeting">
    <literalExpression>
      <text>"Hello " + name</text>
    </literalExpression>
  </decision>
</definitions>
"""

with {:ok, model} <- Boxic.DMN.load_xml(xml),
     :ok <- Boxic.DMN.validate(model, for: :evaluation),
     {:ok, greeting} <- Boxic.DMN.evaluate(model, "Greeting", %{"name" => "Ada"}) do
  greeting
end

Use Boxic.DMN.load_file/1 for a filesystem path. It resolves only declared relative locationURI imports below the root model directory. In-memory XML has no ambient authority; pass an imports: map or resolver: to load_xml/2. The compatibility Boxic.DMN.load/1 function accepts either XML-looking input or a path, but new code should use the explicit functions.

Loading returns {:ok, %Boxic.DMN.Model{}} or a documented load error. Capability validation returns :ok or stable Boxic.DMN.Diagnostic values:

Boxic.DMN.validate(model, for: :evaluation)
Boxic.DMN.validate(model, for: :serialization)
Boxic.DMN.validate(model, for: :authoring)

Use inspect_xml/1 for a best-effort view of older or unsupported documents; inspection does not grant executable or writable status.

Edit and export decision tables

Boxic.DMN.Authoring.DecisionTable provides immutable, ID-based operations for the structural edits a decision-table UI commonly performs. For example:

alias Boxic.DMN.Authoring.DecisionTable, as: Authoring

with {:ok, model} <- Boxic.DMN.load_xml(xml),
     {:ok, model} <-
       Authoring.put_input_entry(model,
         decision_id: "eligibility",
         rule_id: "adult",
         input_id: "customer_age",
         text: ">= 18"
       ),
     :ok <- Boxic.DMN.validate(model),
     {:ok, written_xml} <- Boxic.DMN.encode_xml(model) do
  written_xml
end

Adding, removing, or moving an input or output clause updates the corresponding entry position in every rule. The caller provides stable IDs; Boxic does not generate random identifiers. UI-only draft, selection, undo, and persistence state remains an application concern.

encode_xml/2 emits deterministic DMN 1.5 XML. Its options are:

[format: :pretty | :compact, xml_declaration: true | false]

The defaults are pretty two-space output with an XML declaration, LF line endings, and one final newline. Boxic.DMN.validate_serializable/2 performs the same preflight checks without producing XML.

The writer guarantees semantic rather than byte-identical source round-tripping. A loaded model is rejected when its DMN version differs from the pinned output version or when the loader detected content it could not retain, such as unsupported extensions or DMNDI. This prevents an edit/export workflow from silently discarding authored content.

Focused writer performance can be measured without adding work to the ordinary test suite:

mix run bench/xml_writer_bench.exs

The benchmark covers 100, 1,000, and 10,000-rule tables and reports elapsed time, output size, and process memory.

Maintainers building or publishing this umbrella child as a Hex package must select the published boxic_feel dependency rather than the local sibling:

BOXIC_DMN_HEX_BUILD=true mix hex.build
BOXIC_DMN_HEX_BUILD=true mix hex.publish

Compatibility

Boxic targets DMN 1.5. Against the vendored official DMN Technology Compatibility Kit revision a162739daee85fb28e9d3bec2f306505992dae0f, the DMN suite passes all 1,485 selected cases. This result covers the DMN suite; the separate FEEL suite is reported by boxic_feel.

Evaluator results, strict schema loading, imports, and native writer round trips are recorded as independent evidence. TCK models containing unmodeled extensions or DMNDI remain explicitly non-writable; they are never silently converted or presented as complete interchange coverage.

See CONFORMANCE.md for the public boundary and CONSTRUCT_CAPABILITY_LEDGER.md for the exact modeled, executable, writable, and blocked construct surface.

Java external-function integration is intentionally not implemented because Boxic runs on the BEAM rather than the JVM. Trusted host functions can instead be exposed through Boxic.FEEL.ExternalFunctions.

External functions and trust

Pass an allowlisted external-function registry when evaluating:

Boxic.DMN.evaluate(model, "Price", inputs,
  external_functions: MyApp.DecisionFunctions
)

Boxic.DMN.evaluate_service(model, "Pricing Service", arguments,
  external_functions: MyApp.DecisionFunctions
)

Registry entries execute application code in the evaluator process. Construct registries only from trusted application configuration, never from model content or untrusted strings. The registry is kept outside ordinary FEEL context data. Built-ins win collisions unless the host explicitly passes external_function_precedence: :registered. Applications should isolate or time-limit functions that perform remote or long-running work.

License

Boxic DMN is licensed under Apache-2.0. The official TCK corpus and local compatibility artifacts are not included in the Hex package.