# VS-00 Platform Bootstrap - DATA_CONTRACT

**Version:** 1.0  
**Status:** APPROVED (AEG-VS-00-02)  
**Date:** 2026-08-04  
**Author:** Data Architect/DBA  
**Gateway:** G0 (Platform Foundation)

---

## 1. Acceptance Criteria (from WBS_MASTER.csv)

✅ **Requirement:** published_at/revision/valid-time/hash/단위/격리/재처리와 소유자가 정의되고 overwrite 경로가 없음

---

## 2. Temporal Dimensions (PIT Envelope)

### 2.1 published_at (Publication Timestamp)

| Property | Value |
|----------|-------|
| **Type** | `timestamp without time zone` (UTC) |
| **Nullable** | NO |
| **Default** | `now()` at insert time |
| **Invariant** | `published_at <= now() (at query time)` |
| **Usage** | Point-in-time snapshot marker; used in all queries as `WHERE published_at <= @cutoff` |

**Schema:**
```sql
published_at TIMESTAMP NOT NULL DEFAULT now()
```

**Examples:**
```
✅ 2026-08-04 10:30:45.123 UTC
❌ 2026-08-05 10:30:45.123 UTC (future date forbidden)
```

### 2.2 revision (Data Version)

| Property | Value |
|----------|-------|
| **Type** | `int` (sequential, non-negative) |
| **Nullable** | NO |
| **Range** | 0 to 2,147,483,647 (INT32_MAX) |
| **Increment** | Always increases; never decreases or repeats |
| **Uniqueness** | (aggregate_id, revision) unique constraint |

**Schema:**
```sql
revision INT NOT NULL DEFAULT 1,
CONSTRAINT uk_aggregate_id_revision UNIQUE(aggregate_id, revision)
```

**Invariant:**
```
revision(version_N) > revision(version_N-1)
```

### 2.3 valid-time (Business Validity Window)

| Property | Value |
|----------|-------|
| **Type** | `valid_from TIMESTAMP NOT NULL, valid_to TIMESTAMP NULL` |
| **Semantics** | Period during which this record represents reality |
| **Null Handling** | `valid_to = NULL` means "currently valid" (open-ended) |
| **Non-Overlapping** | For same aggregate_id, valid-time intervals must not overlap |

**Schema:**
```sql
valid_from TIMESTAMP NOT NULL,
valid_to TIMESTAMP NULL,
CONSTRAINT ck_valid_time CHECK (valid_from < valid_to OR valid_to IS NULL),
CONSTRAINT uk_valid_time UNIQUE(aggregate_id, valid_from)
```

**Examples:**
```
Scenario: Interest rate change
- Record 1: valid_from=2026-01-01, valid_to=2026-06-30 (past)
- Record 2: valid_from=2026-07-01, valid_to=NULL (current)
✅ No overlap; continuous coverage
```

---

## 3. Integrity Dimensions

### 3.1 hash (Content Hash)

| Property | Value |
|----------|-------|
| **Type** | `varchar(64)` (SHA-256 hex) |
| **Nullable** | NO |
| **Purpose** | Detect data corruption; enable row-level replay detection |
| **Computation** | `SHA256(serialized_payload)` |

**Schema:**
```sql
content_hash VARCHAR(64) NOT NULL,
INDEX idx_content_hash (content_hash)
```

**Replay Detection (Idempotency):**
```
IF EXISTS (SELECT 1 FROM shadow_runs 
           WHERE aggregate_id = @id 
           AND content_hash = @newHash)
  THEN SKIP (already applied)
ELSE INSERT (new data)
```

### 3.2 단위 (Measurement Unit / Currency)

| Property | Value |
|----------|-------|
| **Type** | `varchar(10)` (code, e.g., 'KRW', 'USD', 'SHARES') |
| **Nullable** | NO |
| **Immutable** | YES; cannot change across revisions for same aggregate |
| **Constraint** | Must match expected unit for field type |

**Schema:**
```sql
unit_code VARCHAR(10) NOT NULL,
CONSTRAINT fk_unit_code FOREIGN KEY (unit_code) REFERENCES ref.units(code),
CONSTRAINT ck_unit_consistency CHECK (unit_code NOT NULL)
```

**Examples:**
```
✅ Field: price, unit: KRW
✅ Field: shares, unit: SHARES
❌ Field: price, unit: SHARES (mismatch)
```

---

## 4. Isolation & Replay

### 4.1 격리 (Isolation Level)

| Property | Value |
|----------|-------|
| **Type** | Snapshot Isolation (SQL Standard: SERIALIZABLE for writes) |
| **Read Consistency** | ✅ No dirty reads, no phantom reads within PIT window |
| **Write Consistency** | Append-only; no UPDATE or DELETE |

**Transaction Pattern:**
```csharp
BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
  -- Verify row doesn't exist (idempotency check via hash)
  IF NOT EXISTS (...) THEN
    INSERT INTO events (...) VALUES (...);
  END IF;
COMMIT;
```

### 4.2 재처리 (Replay)

| Property | Value |
|----------|-------|
| **Pattern** | Idempotent; same input = same result, always |
| **Scope** | (aggregate_id, published_at, revision) uniquely identifies record |
| **Recovery** | If handler crashes, event can be replayed from outbox without duplication |

**Replay Guarantee:**
```
Event(id=123, published_at=T1, revision=R1, hash=H1)
  ├─ Replay 1: Creates row (success)
  ├─ Replay 2: Detects duplicate hash, skips (idempotent)
  └─ Replay N: Always skips (no side effects)
```

---

## 5. Ownership & Mutation Control

### 5.1 소유자 (Owner / Module Authority)

| Property | Value |
|----------|-------|
| **Concept** | Each table/aggregate is owned by exactly one module |
| **Access Pattern** | Only owning module writes; others read via contracts |
| **No Cross-Module Access** | module_A cannot directly INSERT/UPDATE module_B's tables |

**Schema Pattern:**
```sql
-- Table owned by model_operations module
CREATE TABLE model_operations.shadow_runs (
  ...
) TABLESPACE model_ops_space;

-- Only model_operations app-role can INSERT/UPDATE this table
GRANT INSERT, UPDATE ON model_operations.shadow_runs TO role_model_ops_write;
GRANT SELECT ON model_operations.shadow_runs TO public; -- read-only
```

**Cross-Module Read:**
```csharp
// Module: signal_engine (read-only)
// Pattern: Use stored procedure or materialized view, never direct table access
var results = dbContext.ShadowRunsProjection
    .Where(x => x.published_at <= cutoffDate)
    .Select(x => new { x.Id, x.Score })
    .ToList();
```

### 5.2 overwrite 경로 불가 (No Direct Mutation)

| Guarantee | Mechanism |
|-----------|-----------|
| **No UPDATE** | Row state is immutable once inserted |
| **No DELETE** | Historical data is retained for audit trail |
| **No TRUNCATE** | Table can only grow (append-only) |
| **State Changes** | Expressed as new row with incremented `revision` and new `valid_to` |

**Schema Enforcement:**
```sql
-- Revoke all mutation permissions except INSERT
REVOKE UPDATE, DELETE, TRUNCATE ON model_operations.shadow_runs FROM PUBLIC;
REVOKE UPDATE, DELETE, TRUNCATE ON model_operations.shadow_runs FROM role_model_ops_write;

-- Only INSERT is permitted
GRANT INSERT ON model_operations.shadow_runs TO role_model_ops_write;
```

**Example: State Transition (not overwrite)**
```sql
-- OLD: Update is forbidden
UPDATE shadow_runs SET status = 'COMPLETED' WHERE id = 123;  -- ❌ DENIED

-- NEW: Insert new revision (append-only)
INSERT INTO shadow_runs 
  (aggregate_id, revision, published_at, valid_from, status, ...)
VALUES
  (123, 2, now(), now(), 'COMPLETED', ...);  -- ✅ ALLOWED
```

---

## 6. Data Quality Rules (DQ & Lineage)

### 6.1 Completeness

| Field | Nullability | Reason |
|-------|-------------|--------|
| `aggregate_id` | NOT NULL | Identity |
| `revision` | NOT NULL | Version |
| `published_at` | NOT NULL | PIT marker |
| `valid_from` | NOT NULL | Validity window start |
| `valid_to` | NULL OK | Open-ended validity |
| `content_hash` | NOT NULL | Integrity check |
| `unit_code` | NOT NULL (domain-specific) | Measurement unit |
| Domain fields | Domain-specific | Per business rule |

### 6.2 Lineage

| Dimension | Source | Tracking |
|-----------|--------|----------|
| **Data Provenance** | Outbox event → Inbox handler → Write |
| **Audit Trail** | `published_at` + `revision` | Full history |
| **Correlation** | `CorrelationId` in event metadata | End-to-end tracing |
| **Reproducibility** | `content_hash` (deterministic) | Verify no data corruption |

**Lineage Query:**
```sql
SELECT 
  aggregate_id,
  revision,
  published_at,
  valid_from,
  valid_to,
  content_hash,
  'source_system' AS provenance
FROM model_operations.shadow_runs
WHERE aggregate_id = @id
ORDER BY revision ASC;
```

---

## 7. Migration & Schema Versioning

### 7.1 Migration Files

| MIG ID | Purpose | Status |
|--------|---------|--------|
| `MIG-0000` | Create platform bootstrap schema | ✅ Applied |
| `MIG-0013` | Create inbox/outbox tables | ✅ Applied |
| `MIG-00XX` | Future VS-00 extensions | PENDING |

**Location:** `src/KArtSell.DbMigrator/Scripts/`

### 7.2 Schema Evolution

- **Additions:** New columns are backward-compatible (nullable or with defaults)
- **Deprecations:** Columns marked deprecated, not dropped
- **Breaking Changes:** Require version bump + approval

---

## 8. Examples & Use Cases

### 8.1 Query Pattern: PIT (Point-in-Time)

```csharp
// Acceptance Criteria: All reads must include PIT condition
var shadowRun = dbContext.ShadowRuns
    .Where(x => x.PublishedAt <= cutoffDate)  // ✅ PIT condition
    .Where(x => x.AggregateId == modelId)
    .OrderByDescending(x => x.Revision)       // Latest version
    .FirstOrDefault();
```

### 8.2 Insert Pattern: Append-Only with Idempotency

```csharp
public async Task InsertShadowRunAsync(ShadowRunEvent evt)
{
    using var tx = await dbContext.Database.BeginTransactionAsync();
    try
    {
        // Check idempotency: if this exact hash exists, skip
        var isDuplicate = await dbContext.ShadowRuns
            .AnyAsync(x => x.ContentHash == evt.ContentHash);
        
        if (isDuplicate)
            return; // Idempotent: already inserted
        
        // Insert new record
        dbContext.ShadowRuns.Add(new ShadowRun
        {
            AggregateId = evt.ModelId,
            Revision = evt.Revision,
            PublishedAt = DateTime.UtcNow,
            ValidFrom = DateTime.UtcNow,
            ValidTo = null, // Current (open-ended)
            ContentHash = evt.ContentHash,
            UnitCode = "PROBABILITY",
            Status = "RUNNING",
            ...
        });
        
        await dbContext.SaveChangesAsync();
        await tx.CommitAsync();
    }
    catch
    {
        await tx.RollbackAsync();
        throw;
    }
}
```

### 8.3 Historical Query: Audit Trail

```sql
-- Show all revisions of a model's validation history
SELECT 
  revision,
  published_at,
  valid_from,
  valid_to,
  status,
  score
FROM model_operations.shadow_runs
WHERE aggregate_id = '00000000-0000-0000-0000-000000000001'
ORDER BY revision ASC;

/*
Result:
revision | published_at | valid_from | valid_to | status | score
1 | 2026-08-04 09:00 | 2026-08-04 09:00 | NULL | RUNNING | NULL
2 | 2026-08-04 10:30 | 2026-08-04 10:30 | NULL | RUNNING | 0.543
3 | 2026-08-04 11:00 | 2026-08-04 11:00 | NULL | COMPLETED | 0.567
*/
```

---

## 9. Verification (Testing)

### 9.1 Schema Conformance Test

```csharp
[Fact]
public async Task ShadowRunsTable_ConformsToDataContract()
{
    // Verify schema matches contract
    var columnNames = dbContext.Model.FindEntityType(typeof(ShadowRun))!
        .GetProperties()
        .Select(p => p.GetColumnName())
        .ToList();

    Assert.Contains("published_at", columnNames);
    Assert.Contains("revision", columnNames);
    Assert.Contains("valid_from", columnNames);
    Assert.Contains("content_hash", columnNames);
    Assert.Contains("unit_code", columnNames);
}
```

### 9.2 Idempotency Test

```csharp
[Fact]
public async Task Insert_IsIdempotent_SameHashNotDuplicated()
{
    var evt = new ShadowRunEvent { ... };
    
    // Insert twice
    await handler.Handle(evt);
    await handler.Handle(evt);
    
    // Should have only 1 record in database
    var count = dbContext.ShadowRuns
        .Count(x => x.ContentHash == evt.ContentHash);
    
    Assert.Equal(1, count);
}
```

### 9.3 PIT Query Test

```csharp
[Fact]
public async Task Query_WithPitCondition_ReturnsOnlyCutoffData()
{
    // Insert records at different times
    var cutoff = new DateTime(2026, 8, 4, 10, 30, 0);
    
    await dbContext.ShadowRuns.AddRangeAsync(
        new { PublishedAt = cutoff.AddMinutes(-5), ... },  // Before cutoff
        new { PublishedAt = cutoff.AddMinutes(5), ... }    // After cutoff (should not appear)
    );
    await dbContext.SaveChangesAsync();
    
    // Query
    var results = dbContext.ShadowRuns
        .Where(x => x.PublishedAt <= cutoff)
        .ToList();
    
    // Should only return record before cutoff
    Assert.Single(results);
}
```

---

## 10. Sign-Off

| Role | Name | Date | Approval |
|------|------|------|----------|
| **Data Architect/DBA** | (Primary Owner) | 2026-08-04 | ✅ APPROVED |
| **Quant Lead** | (Domain Expert) | 2026-08-04 | ✅ APPROVED |
| **Architect** | (Tech Review) | 2026-08-04 | ✅ APPROVED |

---

## 11. Appendix: Related Documents

- **Migration:** `src/KArtSell.DbMigrator/0000_PlatformBootstrap.sql`
- **Entity Model:** `src/KArtSell.Modules.Host/BuildingBlocks/PlatformBootstrap/Domain/ShadowRun.cs`
- **Query Tests:** `tests/KArtSell.Data.Tests/ShadowRunTests.cs`
- **WBS Requirement:** AEG-VS-00-02 (Gate 0, Priority P0)

---

**Status:** ✅ **APPROVED & ACTIVE**  
**Last Updated:** 2026-08-04  
**Versioning:** This document version controls contract; changes require architect approval
