xgml.org  ·  Open Standard  ·  Apache 2.0

The open proof
exchange standard.

XGML (Extensible Graph Markup Language) defines a structured reasoning contract: claims, evidence, proofs, and Ed25519 signatures that survive model boundaries and regulatory scrutiny.

View Specification GitHub  ↗
2,347
Proof Nodes
Nodes in the Aevion proof graph. 2,274 PROVED. 60 AXIOM. 13 OPEN (Millennium Prize problems only).
1.1MB
Production Graph
Production XGML graph. Generated 2026-04-08. Root hash c340c373.
v1.0.0
Current Spec
Current specification version. Backward-compatible schema.
Apache 2.0
License
Open standard. No royalties. No lock-in.
Node Types

Five first-class graph primitives

Every XGML document is a directed acyclic graph of typed nodes. The type system is closed at v1.0.0 — extensions go through the spec process.

THEOREM
A formally proven mathematical statement. Accompanied by a Lean 4 reference and a checkable proof term.
LEMMA
Supporting result used in theorem proofs. May be reused across multiple theorems within the same graph.
AXIOM
Base assumption, unproven by design. All axioms are declared explicitly — no hidden foundations.
DEFINITION
Structural or type definition. Establishes the vocabulary that theorems and lemmas operate over.
CONJECTURE
Open problem (Riemann, Collatz, etc.). Tracked in the graph with explicit OPEN status and no sorry-hiding.
Schema Sample

A document you can read in 30 seconds

XGML is JSON. No binary encoding, no proprietary tooling. Any language that can parse JSON can read or produce XGML.

{
  "xgml_version": "1.0.0",
  "document_type": "CAUSAL_PROOF_GRAPH",
  "nodes": [{
    "id":      "theorem_bft_safe",
    "type":    "THEOREM",
    "status":  "PROVED",
    "name":    "bft_safe",
    "lean_ref": {
      "file": "Byzantine.lean",
      "line": 42
    }
  }],
  "edges": [{
    "source": "theorem_bft_safe",
    "target": "def_bft_threshold",
    "type":   "DEPENDS"
  }],
  "root_hash": "c340c373...",
  "signature": {
    "algorithm": "Ed25519",
    "issuer":    "Aevion LLC"
  }
}
Implementation

Three implementation tracks

Pick the track that fits your team. All three interoperate — a producer's output validates against the same schema a governance participant helped write.

Track 01
Validator Track

Parse and validate XGML documents against the schema. Confirm that every claimed proof node has a valid Lean reference and that the Ed25519 signature chain is intact.

Track 02
Producer Track

Emit XGML from your Lean 4 corpus or proof system. The reference exporter converts lake build artifacts into signed, graph-structured XGML documents automatically.

Track 03
Governance Track

Participate in spec evolution via GitHub discussions. Propose new node types, edge semantics, or signature schemes through the formal RFC process before they enter the versioned schema.