flo-lang 0.1.4

FLO reference implementation

FLO

FLO is a declarative language for modeling process flow.

It allows you to define processes in a minimal, versioned format and compile them into a canonical graph representation (FLO IR) for visualization and analysis.

User documentation: docs/User_Manual.md

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Development Workflow (uv)

FLO uses uv as the canonical developer tool for environment management, dependency sync, running commands, builds, and publish.

From the repository root:

uv sync --dev

Run FLO locally:

uv run flo render examples/reference/linear.flo

Run quality gates:

uv run pre-commit run --all-files

Build distributions:

uv build

Publish (token auth):

uv publish dist/flo_lang-<version>*
# username prompt: __token__
# password prompt: pypi-<token>

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Example

spec_version: "0.1"

process:
  id: onboarding_v1
  name: Client Onboarding
  version: 1
  owner:
    id: ops_mgr
    name: Ops Manager
  business_units:
    - id: sales
      name: Sales
    - id: ops
      name: Operations

steps:
  - id: start
    kind: start
    name: Start

  - id: collect_docs
    kind: task
    name: Collect Documents
    lane: sales

  - id: verify
    kind: task
    name: Verify Documents
    lane: ops

  - id: approved
    kind: decision
    name: Approved?
    outcomes:
      yes: finish
      no: collect_docs

  - id: finish
    kind: end
    name: Complete

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What FLO Provides

• Deterministic compilation to FLO IR\
• Structural and semantic validation\
• Graph projections: flowchart, swimlane, spaghetti map, SPPM\
• SVG and JSON exports\
• Ingredients list and movement report exports\
• Stable foundation for analytics

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What FLO Does Not Provide

• Workflow execution\
• Task scheduling\
• Orchestration\
• Simulation engines (v0.x)

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Architecture

• src/flo/ --- compiler, validators, renderers, and CLI\
• schema/ --- JSON schemas for FLO IR and types\
• examples/ --- canonical reference examples\
• tests/ --- unit, integration, and conformance tests\
• docs/ --- user manual and design documents

Downstream projects depend on FLO IR.

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Source of Truth Hierarchy

• Structural contract SSOT: schema/flo_ir.json
• Policy authority: docs/policy/authoritative_artifacts.md
• Diagram and artifact specs: docs/specs/
• Core semantic spec: docs/specs/core_language.md
• Historical semantic background note: docs/design/history/IR.md
• User-facing summary: README.md

Hierarchy policy and update workflow are defined in docs/policy/authoritative_artifacts.md.

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Current Semantic Constraints (v0.1)

This is a summary only. Normative semantics live in docs/specs/core_language.md.

• Exactly one start node.
• At least one end node.
• All edge endpoints must resolve to declared node IDs.
• Every non-start node must have at least one predecessor.
• Every non-end node must have at least one successor.
• Every node must be reachable from start.
• Every node must be able to reach at least one end node.
• decision nodes must have at least two outgoing transitions.
• wait_time is valid only on queue nodes.

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Versioning

FLO follows semantic versioning at the spec level.

• v0.x: rapid iteration\
• v1.0: language stability

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Philosophy

FLO treats processes as first-class artifacts:

• Explicit\
• Versioned\
• Portable\
• Validatable

It is a small language by design.

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Schema Contract & Migration

As of v0.1 the compiler emits a schema-shaped canonical IR and the runtime enforces that contract. The compiler must set IR.schema_aligned to True and IR.to_dict() will produce the top-level mapping with process, nodes, and edges fields required by the authoritative JSON Schema in schema/flo_ir.json.

If you are upgrading from an earlier development version that relied on an internal IR translator, update any custom compiler integrations to emit the schema-shaped IR directly. The translator was intentionally removed; CI now validates example outputs using the same schema and will fail when the contract is violated.