Write a Dialect

A Dialect adds architectural meaning to plan or state instances. Start with a small provider case whose exported plan you can inspect. Build Rules from that evidence, not names or a desired diagram shape.

For each Rule, verify:

exact instance eligibility;
architectural classification, emission, or composition it contributes;
source path proving each result.

Start with Read a Rule and Evidence and target resolution if the connection between a provider attribute and an architectural fact is unclear.

Create source root

Dialect package Files

project/
└── dialects/
    └── payments/
        ├── dialect.rf.hcl
        ├── vocabulary.rf.hcl
        ├── network/
        │   └── virtual-network.rf.hcl
        └── presentation.json

Run the commands below from project/. Files can divide the source for review, but one dialect declaration owns the entire recursive source tree.

02
Declare identity and provider
dialects/payments/dialect.rf.hcl RF
1 dialect "payments" { 2 version = "0.1.0" 3 4 provider "hashicorp/aws" { 5 version = "= 6.62.0" 6 } 7 }
A Dialect cannot import another. References can target its own definitions or the embedded RF Vocabulary; Rootform records the latter dependency from rf.* references. The provider constraint should match versions you tested.
03
Add local terms when needed

Use the RF Vocabulary when its terms match what your provider evidence can establish:
- rf.concept.virtual-network and rf.concept.subnet;
- rf.concept.kubernetes-cluster, rf.concept.managed-database, rf.concept.object-storage-container, and rf.concept.service-identity;
- rf.context.network and rf.context.runtime.
Use a local Concept or Context for a term outside that shared vocabulary:
dialects/payments/vocabulary.rf.hcl RF
1 concept "load-balancer" { 2 description = "A load-balancing service." 3 } 4 5 context "project" { 6 description = "Placement in a provider project." 7 }
With the payments owner above, these IDs are payments.concept.load-balancer and payments.context.project. Descriptions document meaning; they do not create architectural facts.

Write a complete Rule

dialects/payments/network/virtual-network.rf.hcl RF

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rule "vpc" {
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  match {
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    kind = "resource"
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    type = "aws_vpc"
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  }
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  as = rf.concept.virtual-network
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  identity {
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    attributes = ["id"]
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  }
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  endpoint {
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    attributes = ["id"]
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  }
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}
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rule "subnet" {
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  match {
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    kind = "resource"
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    type = "aws_subnet"
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  }
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  as = rf.concept.subnet
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  context {
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    as       = rf.context.network
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    to       = rf.concept.virtual-network
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    via      = source.vpc_id
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    on_null  = "absent"
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    on_empty = "absent"
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    match {
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      by       = target.id
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      strategy = "exact"
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    }
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  }
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}

Match-only Rules are invalid. match.kind defaults to resource. match.type must name the exact resource type exposed by the input adapter. where can narrow eligibility with a bounded, typed expression, but an unknown value does not establish a match.

Every observed managed and data instance already has a Representation. A Rule enriches that same instance; lack of a matching Rule never erases it.

05
Add facts and composition deliberately

Use a Context for named placement, a Relation for a directed domain predicate, and a Contribution for support that does not absorb its source. First identify the target Concept or Rule in to, then choose a via path backed by the provider's evaluated value. Set on_null and on_empty on every emission: they say whether those values prove absence or leave the closure indeterminate.

When a value identifies a target by attribute rather than a direct traversal, declare that target's identity attributes on its Rule. List alternative match.by paths in priority order. The supported comparison modes and their limits belong to explicit attribute matching. An unknown, sensitive, incompatible, or ambiguous candidate leaves the closure indeterminate. Do not turn it into a guessed edge.

Use a provider.<path> only when the provider configuration names a managed resource through a direct reference in a paired saved plan. Rootform can follow simple pass-through variables, locals, and module outputs for the planned stage. A literal, transformed expression, state input, historical stage, OpenTofu provider for_each, or JSON configuration syntax provides no such proof; the closure stays indeterminate (unavailable). Rootform does not read literal provider configuration values, whose sensitivity the plan export cannot identify. See traversal evidence.

Allow an external endpoint only when the referenced object may truly be outside the plan's inventory. Choose its identity disclosure level deliberately; it never permits a sensitive value into a Form.

Choose a fact whose meaning matches what the provider evidence proves:
Direct parent proved by a resource reference RF
context { as = context.ownership to = concept.parent via = source.parent_id on_null = "absent" on_empty = "absent" }
- Use an ownership Context for an API or lifecycle parent when the traversal resolves that exact parent. A resource-group name is administrative placement only when the provider contract says the resource is created in that group.
- Use a domain Context such as rf.context.network when the reference proves placement in that domain. It may coexist with administrative ownership.
- Keep an association with several beneficiaries as Contributions when no unique parent exists. If the API independently proves one parent, emit that Context and retain the distinct Contributions.
- Add a Relation only for a documented interaction. A shared traversal may prove both placement and interaction when those facts have different meanings.
For the direct-reference pattern above, a literal has no reference proof. An explicit identity match can establish a known literal value instead. Test missing, unknown, sensitive, transformed and ambiguous evidence beside the successful parent; never add a fallback parent from type or naming.

Composition members are ordered. An unresolved member stays on its root with a reason; dependent later members remain unresolved, while independent ones may resolve. The root keeps its classification and emissions. Members keep their Representations and do not inherit the root Rule or Concept. See Understand composition.
06
Compile and inspect definitions

Check the source before interpreting a plan. The validation result identifies the first invalid path; show then confirms which qualified Rule and Concept the active catalog contains.

The aws_vpc and aws_subnet types also match Rules in embedded aws. A --dialect override adds a source for one command; it does not exclude that embedded owner. For this walkthrough, select payments and exclude embedded aws in the project lock once, before analyzing or testing:
rootform fmt --check ./dialects/payments rootform validate dialects ./dialects/payments rootform validate rule payments.rule.subnet --dialect ./dialects/payments rootform show payments.rule.subnet --dialect ./dialects/payments rootform show rf.concept.subnet rootform add dialects ./dialects/payments rootform remove dialects aws --embedded rootform init . --locked --offline --no-input
Shell
Named commands use owner-first IDs. Bare names work only when unambiguous. The following plan and fixture commands use this recorded selection, without a --dialect override. test reads selection from the directory under test. Use test . from project/ to keep the authoring selection while discovering nested fixtures.
07
Prove consequences with fixtures
Dialect fixture Files
fixtures/payments/minimal/ ├── main.tf ├── plan.json ├── plan.tfplan └── analysis.golden
Export plan.json from a saved plan.tfplan and keep both beside the exact main.tf used to produce them. OpenTofu users run the same commands with tofu. Saved plans and plan JSON can contain secrets in clear text; keep them out of Git and public artifacts. Rootform reads them locally; it never runs Terraform or OpenTofu and never contacts providers. The golden is a Form, not a copy of the plan. Plan inputs covers the export.

Inspect one rootform run fixtures/payments/minimal/plan.json --plan-file fixtures/payments/minimal/plan.tfplan --no-serve result before recording the golden. Look for the expected instance, Rule, facts, and closure outcomes; a successful exit alone does not prove the Rule created the intended fact. Then record or compare fixtures:
rootform test . --update rootform test . rootform test . --run payments/minimal
Shell
--update writes the expected Form for review. The next command compares the Form of a real run against it; status 0 means every selected case passed, 1 means a case differed, and 3 means rootform.lock is invalid or no case matched. --run narrows cases by name. Review the golden diff before accepting a changed Rule. A --dialect override lasts one command and leaves rootform.lock unchanged; run, test, validate, list, show, and explain accept it. This walkthrough uses the lock because it must exclude the overlapping embedded owner.

Keep presentation separate

Optional presentation.json maps source resource identities independently of Rule coverage. It can also assign icons and labels to Rules and Concepts:

dialects/payments/presentation.json JSON

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{
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  "format_version": "1",
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  "resources": {
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    "resource/aws_vpc": "generic/network",
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    "resource/aws_subnet": "generic/subnet"
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  },
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  "rules": {
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    "vpc": "generic/network",
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    "subnet": "generic/subnet"
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  },
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  "concepts": {},
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  "resource_labels": {
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    "resource/aws_vpc": "Amazon VPC",
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    "resource/aws_subnet": "Amazon VPC subnet"
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  },
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  "rule_labels": {
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    "vpc": "Amazon VPC",
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    "subnet": "Amazon VPC subnet"
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  },
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  "concept_labels": {}
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}

Resource mappings work even when a resource type has no Rule. The manifest accepts no SVG, HTML, URLs, styling, layout, architectural facts, or behavior. Normal runs warn and ignore invalid presentation; rootform package dialects rejects it. See presentation contract.

09
Package and publish a Dialect

Packaging stays local and offline. This example binds the payments owner to the AWS provider; the owner and provider are separate identities. Package the same source root you validated and tested:
rootform package dialects ./dialects/payments --to artifacts/oci \ --source-url https://example.com/team/dialects \ --documentation-url https://example.com/team/dialects/docs \ --licenses MPL-2.0
Shell
The result names the packaged Dialect and local destination. Before publishing, record the reviewed source revision with --revision when your publication process requires that provenance. Packaging itself sends nothing to a registry. Generic publication is separate:
rootform publish dialects artifacts/oci \ --to registry.example.com/team/dialects
Shell
Rootform has no official Dialect index or mutable discovery tag.
10
Use a published Dialect

Continue from the same project/ directory with its plan fixture and lock. Replace the local payments selection with the published reference. The lock keeps the exclusion of embedded aws, so its Rules do not overlap with the published Dialect:
rootform remove dialects payments rootform add dialects \ registry.example.com/team/dialects:dialect-payments-0.1.0 rootform init . --locked --no-input rootform run fixtures/payments/minimal/plan.json \ --plan-file fixtures/payments/minimal/plan.tfplan \ --require-enrichment --project . --locked --no-serve -o published-form.json
Shell
Inspect published-form.json for the same payments Rules and facts you reviewed before packaging. Rootform uses the recorded published identity; the local source directory no longer controls this run.

The reference is illustrative; use the published reference you reviewed. Run add from the same project root that init and run use. Set DOCKER_CONFIG before acquisition if the registry needs credentials. init acquires only recorded exact pins. See External content storage for locations.

See Test and validate, Dialect reference, and Rules.

Write a Dialect

Create source root

Declare identity and provider

Add local terms when needed

Write a complete Rule

Add facts and composition deliberately

Compile and inspect definitions

Prove consequences with fixtures

Keep presentation separate

Package and publish a Dialect

Use a published Dialect