# Assertion

**Last Updated:** 2026-01-31
**Confidence:** High

## Summary

The Assertion is the atomic unit of Episteme. It represents a signed claim about reality, not a mutable fact.

**Key Facts:**
- Immutable once written (append-only)
- Content-addressed by BLAKE3 hash
- Contains: subject, predicate, object, lifecycle, source, signatures, timestamp
- Lifecycle stage distinguishes proposals from production-ready truth
- Optionally includes vector embedding for semantic search

**File Pointer:** `crates/stemedb-core/src/types.rs`

## Structure

```rust
pub struct Assertion {
    // The Fact (What)
    pub subject: EntityId,      // "Tesla_Inc"
    pub predicate: RelationId,  // "has_revenue"
    pub object: ObjectValue,    // Text, Number, Boolean, or Reference

    // Lineage (Why)
    pub parent_hash: Option<Hash>,  // Fork pointer
    pub source_hash: Hash,          // Evidence pointer (PDF/URL hash)
    pub visual_hash: Option<PHash>, // Perceptual hash for visual anchoring
    pub epoch: Option<EpochId>,     // Paradigm context
    pub lifecycle: LifecycleStage,  // Proposed, UnderReview, Approved, Deprecated, Rejected

    // Meta-Cognition (Who/How sure)
    pub signatures: Vec<SignatureEntry>, // Multi-sig support
    pub confidence: f32,            // 0.0 to 1.0
    pub timestamp: u64,             // Wall clock time
    pub vector: Option<Vec<f32>>,   // Semantic embedding
}
```

## Lifecycle Stages

```rust
enum LifecycleStage {
    Proposed,    // Initial idea, RFC, suggestion
    UnderReview, // Under active debate
    Approved,    // Production ready, safe for implementation
    Deprecated,  // Was true, now superseded
    Rejected,    // Considered and declined
}
```

New assertions default to `Proposed`. Lifecycle transitions are implemented as new assertions with `parent_hash` pointing to the previous version.

## Identity

Assertion ID = BLAKE3(serialized assertion bytes)

Content-addressed: same content = same hash.

## Related Topics

- [Lifecycle Stages](./lifecycle.md)
- [Storage Layout](./storage.md)
- [Lens Resolution](./lens.md)