HarnessXML#

<p class="mission">HarnessXML is the Open Specification for Executable Intelligent System Workflows.</p>

An intelligent system is rarely one model or one program. It is a workflow: a graph of steps that call models, move data, drive machines, wait on people, fail, retry and compensate. That graph is the real design — and on most teams it exists only as a diagram on a wall and a pile of orchestration code that has drifted away from it.

HarnessXML makes the graph the artifact. One document describes the workflow completely enough to execute, validate, version, sign and audit — and it is portable across the tools and runtimes that read it.

Read the specification Start with the concepts Download schemas & tools

The three ideas#

The visual graph is the authoritative design

People reason about workflows as pictures. The diagram is not documentation of the system — it is the system's design, and it should stay that way.

HarnessXML is the portable representation

A machine-readable form of that design: complete, diffable, reviewable in a pull request, and readable by any tool that implements the specification.

The runtime executes the specification

The same document produces the same execution semantics on any conforming runtime. Behaviour is defined by the specification, not by one vendor's engine.

How the pieces fit#

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<g stroke="currentColor" stroke-width="1.2" stroke-dasharray="4 4" opacity=".45" fill="none"> <path d="M392 98 V140"/> <path d="M120 140 H820"/> <path d="M120 140 V126"/> <path d="M820 140 V126"/> </g> <text x="470" y="164" text-anchor="middle" font-size="12" fill="currentColor" opacity=".75"> anyone may build an editor, parser, validator, runtime, compiler or SDK against the specification </text> <text x="470" y="184" text-anchor="middle" font-size="11.5" fill="currentColor" opacity=".55"> Rumima Enterprise Studio is VisML's commercial authoring environment — one implementation, not the definition </text> </svg> </div>

Rumima is the flagship commercial visual designer for HarnessXML. HarnessXML is not Rumima's file format. The specification is open and vendor-neutral: build your own editor, parser, validator, runtime, compiler, importer, exporter or SDK against it, commercially, without asking permission. If the specification and Rumima ever disagree, the specification is right and Rumima has a bug.

What a document looks like#

xml

<harness xmlns="https://harnessxml.com/spec/1.0"
         id="document_triage" specVersion="1.0" entry="receive">

  <resources>
    <resource id="classifier" type="model" provider="anthropic">
      <property name="model" value="claude-opus-5"/>
      <credential ref="ANTHROPIC_API_KEY" store="vault"/>
    </resource>
  </resources>

  <nodes>
    <node id="receive" type="source" impl="intake.receive">
      <outputs><output name="document" type="binary"/></outputs>
    </node>

    <node id="classify" type="inference">
      <inputs><input name="document" type="binary"/></inputs>
      <outputs>
        <output name="category"   type="string"/>
        <output name="confidence" type="number"/>
      </outputs>
      <resourceRef ref="classifier" role="model"/>
      <retry maxAttempts="4" backoff="exponential" retryOn="rate_limit transient"/>
      <timeout duration="PT3M" onTimeout="retry"/>
    </node>

    <node id="route" type="decision">
      <cases>
        <case when="${classify.confidence >= 0.90}" to="auto_file"/>
        <otherwise to="human_review"/>
      </cases>
    </node>
  </nodes>

  <edges>
    <edge from="receive"  to="classify" type="data" fromPort="document" toPort="document"/>
    <edge from="classify" to="route"    type="control"/>
  </edges>
</harness>

Nothing above is a hint to a human reader. The retry policy, the timeout, the confidence threshold and the escalation path are all executable — and all reviewable in a diff before they reach production.

What it is for#

AI orchestration & agent systems

Model calls, tool use, confidence gating, human escalation, and the retry and rate-limit behaviour that decides whether any of it survives contact with a real API.

Machine learning pipelines

Datasets and models as first-class, digest-identified artifacts, so a run is reproducible and a result is traceable to the inputs that produced it.

Robotics

Bounded loops, non-idempotent physical actions that must never be blindly retried, and compensation paths that put the part back.

Network & industrial automation

Staged rollouts, quorum gates, and a declared rollback for every push — so the undo path is in the design instead of in a runbook at 02:00.

Business process automation

Approval routing, separation of duties, and an audit trail that ties an execution back to the exact design revision that authorised it.

Whatever comes next

The specification describes the workflow and stops at the boundary of what a step does — which is why it does not go stale when the steps change.

Openness is structural, not a slogan#


Specification text	CC BY 4.0 — copy, translate, quote, build on it, commercially, with attribution
Reference code, schemas, examples	Apache 2.0, including an express patent grant
Implementing it	No permission, no royalty, no notification, no agreement to sign
Released versions	Frozen at a permanent URL, forever. Corrections are dated errata, never edits
Changes	Public proposals, 30-day minimum review, rejected proposals stay published
Conformance	Defined by a published test suite, not by agreement with any implementation

Read the governance model — including the conflict of interest VisML has, and the structural limits placed on it.