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FDS Overview

The Fitness Data Standard (FDS) defines an open, interoperable format for exchanging fitness domain data across applications and platforms.

Purpose & Scope​

Enable data portability and interoperability across fitness applications by providing:

  • Normative JSON Schemas for core fitness entities
  • High-quality RFCs with examples and implementation guidance
  • Flexible platform taxonomies via well-defined extension points

Current Scope​

In scope:

  • Exercise data model (RFC-001)
  • Registry entities: Equipment (RFC-002), Muscles (RFC-003), Muscle Categories (RFC-004), Body Atlas (RFC-005)

Out of scope (for now):

  • Workout/programming models
  • User progress tracking
  • Authentication/Authorization

These will be covered by future RFCs.

Versioning & Compatibility​

FDS follows Semantic Versioning for data model releases:

  • Major (X.0.0): Breaking changes to required fields or semantics
  • Minor (0.Y.0): Backward-compatible additions (optional fields, new enum values, documentation clarifications)
  • Patch (0.0.Z): Non-functional changes (typos, editorial, schema metadata)

Compatibility Rules​

  • Data valid in X.Y.Z MUST remain valid in X.(Y+1).0
  • Adding new required fields constitutes a MAJOR change
  • Deprecated fields remain functional throughout the major version
  • Producers and consumers SHOULD use schemaVersion to route validation and logic

Conformance​

Conforming Producer​

  • MUST produce JSON that validates against the FDS JSON Schema for the declared schemaVersion
  • MUST use UUIDv4 for all identifiers in production data
  • MUST populate all required fields and adhere to enumerations and structural constraints
  • SHOULD include schemaVersion and maintain accurate metadata timestamps (RFC 3339, UTC)

Conforming Consumer​

  • MUST validate incoming data against the appropriate schema version
  • MUST ignore unknown fields under attributes/extensions
  • SHOULD tolerate additional optional fields added in newer minor versions
  • SHOULD reject data with missing required fields or invalid enumerations

Next Steps​