# Episteme (StemeDB) Architecture

> **Design Philosophy:** Immutable History, Probabilistic Resolution, Materialized Speed.
> **Status:** Implementation v1.0

## 1. System Overview

Episteme is a **Log-Structured, Content-Addressed Knowledge Graph**. Unlike traditional databases that mutate state in place, Episteme appends **Assertions** to an immutable ledger (Merkle DAG). State resolution happens via **Lenses**.

> **Caveat:** Aphoria's scan observations flow through this append-only path today. Aphoria's authored claims (`AuthoredClaim`) do not -- they are stored in a mutable TOML file (`.aphoria/claims.toml`) and bypass the WAL/Merkle DAG entirely. Routing claims through StemeDB as proper Assertions is a planned gap closure.

To solve the O(N) read latency of conflict resolution, Episteme employs a **Materialized View** layer that pre-calculates the "Current Truth" for standard lenses.

### High-Level Data Flow

```ascii
[Writer Agent]      [Reader Agent]
      │                   ▲
      │ (1) Sign &        │ (6) Sub-millisecond Answer
      │     Propose       │     (Pre-computed)
      ▼                   │
┌────────────┐      ┌────────────┐
│  Ingestion │      │ Resolution │
│  Gateway   │      │ Engine     │
└─────┬──────┘      └─────┬──────┘
      │ (2) Append        │ (5) Apply Lens + Trust Pack
      │     to Ballot     │     (BitSet Filter)
      ▼                   │
┌────────────┐      ┌────────────┐
│ Quarantine │      │ Indexing   │
│ Journal    │──────► Service    │
└─────┬──────┘ (3)  └─────┬──────┘
      │                   │ (4) Compaction & Materialization
      ▼                   ▼
┌────────────┐      ┌────────────┐
│ Job Manager│      │ Materialized│
└────────────┘      │ Views      │
 (TAN Meter)        └────────────┘
```

---

## 2. Core Data Structures

### 2.1. The Atomic Unit: `Assertion` (The Candidate)
Assertions are proposals of truth. They are immutable.

```rust
struct Assertion {
    pub subject: EntityId,
    pub predicate: RelationId,
    pub object: Value,
    pub epoch: Option<EpochId>,
    pub agent_id: PublicKey,     // The Proposer
    pub timestamp: u64,
    // ... lineage and vector fields ...
}
```

### 2.2. The Ballot Box: `Vote` (The High-Velocity Stream)
To prevent lock contention on Assertions, Agents write **Votes** to a separate high-velocity log.

```rust
struct Vote {
    pub assertion_hash: Hash,    // What are we voting on?
    pub agent_id: PublicKey,     // Who is voting?
    pub weight: f32,             // 0.0 - 1.0 (Confidence)
    pub signature: Signature,    // Cryptographic proof
    pub timestamp: u64,
}
```

### 2.3. The Trust Pack (The Overlay)
A curated list of trusted agents, used to filter consensus efficiently.

```rust
struct TrustPack {
    pub id: PackId,
    pub name: String,
    pub maintainer: PublicKey,
    pub agents: BitSet, // BloomFilter or RoaringBitmap for fast intersection
}
```

### 2.4. The Storage Layout (Hybrid Store)

Episteme uses a **Hybrid Storage** architecture to balance write throughput and read latency:
*   **Fjall (LSM-Tree):** Used for write-heavy, append-only data (Assertions, Votes, WAL).
*   **Redb (B-Tree):** Used for read-heavy, random-access data (Indexes, Materialized Views).

| Key | Value | Purpose | Backend |
| :--- | :--- | :--- | :--- |
| `H:{Hash}` | `Assertion` | Immutable Content Store | Fjall |
| `V:{Hash}` | `List<Vote>` | The Ballot Box (Append-only) | Fjall |
| `MV:{Subject}:{Predicate}` | `Assertion` | **Materialized View** (The "Winner") | Redb |
| `TP:{PackID}` | `TrustPack` | Curation Lists | Redb |
| `S:{Subject}` | `List<Hash>` | Adjacency Index | Redb |

---

## 3. The Write Path (The Ballot Box)

1.  **Ingest:** Agents submit `Assertions` or `Votes`.
2.  **Journal:** Written to `episteme-wal` (Quarantine Pattern).
3.  **Ballot Box:** Votes are appended to the `V:{Hash}` stream.
4.  **Compactor (Async):** A background worker aggregates Votes + TrustRank to update the `MV` key.

---

## 4. The Read Path (The Cortex)

**Fast Path (Standard Lenses):**
*   Query: `GET /query?lens=Consensus`
*   Action: `GET MV:{Subject}:{Predicate}`
*   Cost: **O(1)**. Low latency.

**Trusted Path (Trust Packs):**
*   Query: `GET /query?lens=Authority&trust_pack=Science_Pack`
*   Action:
    1.  Fetch Candidate Assertions.
    2.  Fetch Votes.
    3.  **Filter:** Intersect Votes with `TrustPack.agents` (BitSet operation).
    4.  Sum weights of remaining votes.
*   Cost: **O(1)** (if Materialized per Pack) or **O(M)** (Fast calculation).

### Standard Lenses (Implemented)
*   **Consensus:** Highest cluster density (Vote-aware).
*   **Authority:** Filter by **Trust Pack** and **TrustRank**.
*   **Recency:** Last Writer Wins (Hybrid Logical Clock).
*   **EpochAware:** Validates against current paradigm.
*   **Skeptic:** Surfaces conflicts and divergence.

---

## 5. The Meter (Economic Safety)

To prevent infinite loops, the Job Manager enforces **Temporal Advantage Normalization (TAN)**.
*   **Budgeting:** Every Job must declare a `max_cost`.
*   **Throttling:** Forking Reality or Deep Recursion is rejected if `current_cost + projected_cost > max_cost`.

---

## 6. The Simulator (Mid-Training Pipeline)

The system continuously exports data to train the next generation of Agents.
*   **Negative Samples:** High-confidence assertions that were later superseded (Failures).
*   **Golden Paths:** Branches that successfully merged to Main (Successes).
*   **Format:** Exported as HuggingFace-compatible datasets for LoRA fine-tuning.

---

## 7. Implementation Roadmap

### Phase 1: The Spine (Foundation)
*   [x] Reuse `quarantine-journal` pattern for WAL (`stemedb-wal`).
*   [x] Implement `Assertion`, `Epoch`, and **`Vote`** structs (`stemedb-core`).
*   [x] Hybrid Storage backend (`stemedb-storage`).

### Phase 2: The Lattice (Connectivity)
*   [x] **The Ballot Box**: Separate Vote storage stream.
*   [x] **Materializer**: Background worker to maintain `MV` keys.
*   [x] **Trust Packs**: Agent sets for filtering.
*   [ ] **The Meter**: Implement Budget/TAN middleware in Job Manager.
*   [ ] **Agent Wallet**: Sidecar for key management/signing.

### Phase 3: The Cortex (Reasoning)
*   [x] **Lenses**: `Recency`, `Consensus`, `Authority`, `Skeptic` implemented (`stemedb-lens`).
*   [ ] SMT Backend & Branching.
*   [ ] Vector Search.
*   [ ] **Lens: Constraints**: Implement the pre-flight check logic.

### Phase 4: The Hive (Learning)
*   [ ] **The Simulator**: Log exporter pipeline.
*   [ ] **Trust Marketplace**: API for publishing/subscribing to Trust Packs.
*   [ ] **The Super Curator**: Implement "Judge" agent with Visual Anchoring.
