Language reference

Rootform language is a closed, statically validated language for two jobs:

• Dialects interpret managed and data resource instances from plan JSON or state JSON.
• Policy Packs evaluate the resulting architecture without reading raw infrastructure values.

HCL supplies lexical syntax for .rf.hcl and .rf.json. Rootform defines the accepted blocks, attributes, expressions, references, types, defaults, and runtime meaning. General HCL or Terraform expressions are not implicitly part of RF.

This reference documents Rootform language version 0.1.0 and is normative. For motivation and worked examples, start with the learning path.

How to use this reference

Source units

Page	Contract covered
Syntax and files	Source discovery, native and JSON syntax, structural grammar, names, versions, and source-unit boundaries
Symbols and references	Canonical IDs, local and qualified references, resolution, and duplicate rules
RF Vocabulary	Complete embedded rf.* vocabulary and exact meanings

Dialects

Page	Contract covered
Dialect declarations	dialect, provider, concept, context, and relation
Rules and matching	rule, match, managed and data instance kinds, predicates, and selection
Fact emissions	context, relation, contribution, explicit attribute matching, and omissions
Composition	Ordered members, per-instance resolution, and unresolved-member reasons

Expression language

Page	Contract covered
Expressions	Literal types, expression grammars, operators, precedence, and rejected syntax
Traversals and scope	source, provider, target, member, path steps, and position rules
Built-ins	Complete signatures and parameters for exists, length, and architecture queries

Policies

Page	Contract covered
Policy Packs	policy_pack, policy, target, linking, messages, and target intersections
Evaluation	Rule precedence, three-valued evidence, query completeness, outcomes, and exit status

Diagnostics and limits: Stable codes, severity, source ranges, and all author-facing bounds

Construct index

Cardinality applies across one source root unless a placement says otherwise.

Construct	Source unit	Placement	Cardinality	Label	Detail
dialect	Dialect	Top level	Exactly 1	Required	Dialect declarations
provider	Dialect	Inside dialect	0 or more; at least 1 when unit has a Rule	Required	Provider block
concept	Dialect	Top level	0 or more	Required	Semantic definitions
context definition	Dialect	Top level	0 or more	Required	Semantic definitions
relation definition	Dialect	Top level	0 or more	Required	Semantic definitions
rule	Dialect	Top level	0 or more	Required	Rules
identity	Dialect	Inside rule	0 or 1	Forbidden	Identity and endpoint declarations
endpoint	Dialect	Inside rule	0 or 1	Forbidden	Identity and endpoint declarations
Rule match	Dialect	Inside rule	Exactly 1	Forbidden	Matching
context emission	Dialect	Inside rule	0 or more	Optional, exclusive with as	Context emission
relation emission	Dialect	Inside rule	0 or more	Optional, exclusive with as	Relation emission
contribution emission	Dialect	Inside rule	0 or more	Forbidden	Contribution emission
Fact match	Dialect	Inside an emission	0 or 1	Forbidden	Explicit attribute match
composition	Dialect	Inside rule	0 or 1	Forbidden	Composition
member	Dialect	Inside composition	1 or more	Required	Member
Member match	Dialect	Inside member	Exactly 1	Forbidden	Member matching
policy_pack	Policy Pack	Top level	Exactly 1	Required	Policy Pack manifest
policy	Policy Pack	Top level	0 or more	Required	Policy
target	Policy Pack	Inside policy	Exactly 1	Forbidden	Target

Closed expression surface

Area	Accepted values
Literal values	String, Boolean, non-negative number literal with exact signed 64-bit integer value
Unary operators	!
Binary operators	&&, ||, ==, !=, <, <=, >, >=
Traversal roots	source, provider, target, member.<name>, each restricted by position
Policy wrappers	exists(query), length(query)
Policy queries	contexts(...), relations(...), contributions(...)

where and assert do not accept collections, object values, null, floating-point values, arithmetic, conditionals, comprehensions, splats, dynamic indexes, or arbitrary function calls. Static string fields use result-based constant HCL evaluation, and dedicated Policy target fields accept closed list syntax.

Reference conventions

Parameter tables use these meanings:

Term	Meaning
Required	Author must provide value or block.
Optional	Author may omit value or block.
Default	Value compiler uses when optional attribute is absent.
Static	Value must evaluate in empty HCL context; variables and runtime data are unavailable.

Unknown attributes, blocks, functions, and expression shapes fail closed with a diagnostic. They are never preserved for later evaluation.