DMN agent card

Write a Camunda 8 DMN decision table with @bpmnkit/core in one script: create, export, edit, validate. Run it with node --experimental-strip-types build.ts (Node 22.6+) or npx tsx build.ts. Never write DMN XML by hand.

Minimal DMN build script: create, export, edit, validate

import { readFileSync, writeFileSync } from "node:fs"
import { Dmn, exportDmnPreserving } from "@bpmnkit/core"

// 1. Create. "risk" is the decision id a BPMN businessRuleTask references as decisionId.
const definitions = Dmn.createDecisionTable("risk")
	.name("Order risk")
	.hitPolicy("FIRST")
	.input({ label: "Amount", expression: "amount", typeRef: "number" })
	.input({ label: "Country", expression: "country", typeRef: "string" })
	.output({ label: "Risk", name: "risk", typeRef: "string" })
	.rule({ inputs: ["> 1000", "-"], outputs: ['"high"'], description: "Large order" })
	.rule({ inputs: ["-", 'not("DE", "AT")'], outputs: ['"medium"'] })
	.rule({ inputs: ["-", "-"], outputs: ['"low"'] })
	.build()

// 2. Export.
writeFileSync("risk.dmn", Dmn.export(definitions))

// 3. Edit an existing file: parse, change, write with exportDmnPreserving to keep the diagram.
const original = readFileSync("risk.dmn", "utf8")
const edited = Dmn.parse(original)
const decision = edited.decisions.find((d) => d.id === "risk")
if (decision) decision.name = "Order risk level"
writeFileSync("risk.dmn", exportDmnPreserving(original, edited))

// 4. Validate: it parses back and the decision id the process calls is there.
const check = Dmn.parse(readFileSync("risk.dmn", "utf8"))
if (!check.decisions.some((d) => d.id === "risk")) {
	console.error("decision 'risk' missing")
	process.exit(1)
}

npm i @bpmnkit/core. The script writes risk.dmn with its diagram, re-opens it, renames the decision without touching the layout, and checks the decision id.

Several decisions in one file: Dmn.drd()

import { writeFileSync } from "node:fs"
import { Dmn } from "@bpmnkit/core"

// Two decisions in one file: "approval" reads the result of "riskScore".
const drd = Dmn.drd("Order approval")
const riskScore = drd.decision("riskScore", (t) =>
	t
		.name("Risk score")
		.hitPolicy("FIRST")
		.input({ label: "Amount", expression: "amount", typeRef: "number" })
		.output({ label: "Risk", name: "risk", typeRef: "string" })
		.rule({ inputs: ["> 1000"], outputs: ['"high"'] })
		.rule({ inputs: ["-"], outputs: ['"low"'] }),
)
drd.decision(
	"approval",
	(t) =>
		t
			.name("Approval")
			.input({ label: "Risk", expression: "risk", typeRef: "string" })
			.output({ label: "Approved", name: "approved", typeRef: "boolean" })
			.rule({ inputs: ['"low"'], outputs: ["true"] })
			.rule({ inputs: ["-"], outputs: ["false"] }),
	{ requires: [riskScore] }, // pass the handle; a name or label is a type error
)
writeFileSync("approval.dmn", drd.toXml())

drd.decision(id, table, { requires }) returns a handle; requires takes handles (or drd.inputData(id, name) handles), never names. A requires that points at an unknown id throws at build()/toXml().

Top builder options

• Dmn.createDecisionTable(decisionId) … .build() returns DmnDefinitions; Dmn.export(defs) gives the XML with DMNDI shapes.
• .name(text) is the display name; .hitPolicy("UNIQUE" | "FIRST" | "ANY" | "COLLECT" | "RULE ORDER" | "OUTPUT ORDER" | "PRIORITY").
• .input({ label, expression, typeRef }): expression is a FEEL expression over process variables (amount, order.total).
• .output({ label, name, typeRef }): name is the key in the result.
• .rule({ inputs, outputs, description }): one entry per column, in column order, or build throws.
• typeRef: "string" | "number" | "boolean" | "date".
• Read or change an existing file: Dmn.parse(xml) → defs.decisions[i].decisionTable.

Traps

• The process calls the decision id. A BPMN businessRuleTask(id, { decisionId: "risk", resultVariable: "risk" }) must use the argument of createDecisionTable("risk"), not the DMN definitions id, the file name or .name(). Ids are unique across the cluster: a second file with decision risk deploys as a new version of the same decision.
• Deploy the .dmn before an instance reaches the task. The call binds to the latest deployed version: casen deploy deploy risk.dmn first.
• Hit policy UNIQUE is the default. Two matching rules is a runtime incident. Use FIRST for a catch-all last row, or COLLECT for a list.
• Input entries are FEEL unary tests, outputs are FEEL expressions, and neither starts with =. - matches anything; > 1000, [1..10], "DE", not("DE", "AT"). A string output needs quotes: '"high"', not "high".
• Result shape. With one output column the result variable holds the value; with several it holds an object keyed by output name; COLLECT gives a list.
• Edit with the preserving writer. Write exportDmnPreserving(original, edited); Dmn.export alone reformats the file and its diagram.

Validate

casen check risk.dmn order.bpmn --deploy   # DMN lint + every decisionId in the BPMN resolves

casen check <files...> takes .bpmn, .dmn and .form together and exits 1 on errors; add --json for an agent loop. The script above also re-parses the file and checks the decision id.

Related cards: casen agent-card bpmn, casen agent-card form. More: npx bpmnkit-docs ask "decision table hit policy".