# Architecture Decision: eMoney vs ISO-4217 W Tokens

**Date**: Architecture Clarification  
**Status**: ✅ DECISION MADE  
**Impact**: CRITICAL - Unblocks all integrations

---

## Executive Decision

**ISO-4217 W Tokens and eMoney Tokens are SEPARATE, INDEPENDENT systems with DIFFERENT purposes:**

1. **eMoney Tokens**: Regulated digital instruments for collateralized credit issuance (M1 credit layer)
2. **ISO-4217 W Tokens**: Direct 1:1 fiat-backed redeemable instruments (M1 cash layer)

## Detailed Classification

### eMoney Tokens (Vault System)

**Purpose**: 
- Represent borrowed credit against collateral
- Issued through vault system when borrowing
- NOT directly backed by fiat reserves
- Backed by collateral (ETH) in XAU terms

**Characteristics**:
- Classification: M1 eMoney (credit instrument)
- Legal Tender: NO
- Synthetic: NO (but credit instrument)
- Commodity-Backed: NO (but collateralized)
- Backing: Collateral (ETH) → XAU → Credit issuance
- Money Multiplier: Variable (based on collateral ratio, up to 5x credit multiplier)
- Transfer Restrictions: Yes (via ComplianceRegistry and PolicyManager)

**Use Cases**:
- Borrowing against vault collateral
- Debt representation (Debt Tokens minted)
- Settlement instrument for regulated entities

### ISO-4217 W Tokens (W Token System)

**Purpose**:
- Direct 1:1 digital representation of fiat currency
- Fully backed by fiat reserves in custodial accounts
- Redeemable on-demand at par
- NO credit component

**Characteristics**:
- Classification: M1 eMoney (cash instrument)
- Legal Tender: NO
- Synthetic: NO
- Commodity-Backed: NO
- Backing: 1:1 fiat currency in segregated custodial accounts
- Money Multiplier: m = 1.0 (hard-fixed, no fractional reserve)
- Transfer Restrictions: Minimal (may use ComplianceRegistry for policy enforcement, not for credit restrictions)

**Use Cases**:
- Digital cash equivalent
- On-demand redemption
- Settlement for regulated entities
- Bridge transfers

## Relationship Matrix

| Feature | eMoney Tokens | ISO-4217 W Tokens |
|---------|--------------|-------------------|
| **Backing** | Collateral (ETH) | Fiat reserves (1:1) |
| **Money Multiplier** | Variable (up to 5x) | Fixed (1.0) |
| **Issuance** | Through vault borrowing | Through verified fiat settlement |
| **Redemption** | Repay debt | On-demand fiat redemption |
| **Transfer Restrictions** | Yes (PolicyManager, ComplianceRegistry) | Optional (minimal) |
| **Debt Component** | Yes (Debt Tokens) | No (cash only) |
| **GRU Relationship** | Can use GRU triangulation | Isolated from GRU |
| **Bridge Compatibility** | Yes (with restrictions) | Yes (with reserve verification) |

## Integration Rules

### Rule 1: W Tokens CANNOT be eMoney Tokens
- W tokens are NOT a subset of eMoney
- W tokens use separate token contracts
- W tokens have separate compliance rules

### Rule 2: W Tokens CAN be used as Vault Collateral
- W tokens (e.g., USDW) can be deposited as M0 collateral
- Treated as fiat-equivalent collateral
- Valuation: 1 USDW = 1 USD (already in base currency terms)

### Rule 3: eMoney Tokens CANNOT be W Tokens
- eMoney tokens represent credit, not cash
- eMoney tokens are not 1:1 backed by fiat
- eMoney tokens have different backing mechanism

### Rule 4: Both Systems Can Use ComplianceRegistry
- W tokens: Optional use for transfer policy enforcement
- eMoney tokens: Required use for credit restrictions
- Both can use RegulatedEntityRegistry for entity eligibility

## Implementation Decisions

1. **Separate Token Contracts**: ✅ Implemented (ISO4217WToken.sol separate from eMoneyToken.sol)
2. **Separate Compliance**: ✅ Implemented (different compliance rules)
3. **Separate Registries**: ✅ Implemented (TokenRegistry for W tokens, separate from eMoney)
4. **Shared ComplianceRegistry**: ✅ Can share eMoney ComplianceRegistry for transfer restrictions if needed
5. **Vault Collateral**: ⏳ To be implemented (W tokens as approved collateral)

## Integration Points

### Allowed Integrations

✅ **W Tokens → Vault Collateral**: Allowed
- USDW, EURW, etc. can be deposited as collateral
- Treat as fiat-equivalent asset
- No additional XAU conversion needed (already in base currency)

✅ **W Tokens → Bridge**: Allowed
- W tokens can be bridged
- Reserve verification required before bridging
- Compliance checks required

✅ **eMoney Tokens → Vault Borrowing**: Allowed
- eMoney tokens can be borrowed through vaults
- Debt Tokens minted
- Compliance checks required

✅ **eMoney Tokens → Bridge**: Allowed
- eMoney tokens can be bridged
- Transfer restrictions enforced via PolicyManager
- Compliance checks required

### Prohibited Integrations

❌ **W Tokens → eMoney System**: Not allowed
- W tokens cannot be treated as eMoney tokens
- Separate token contracts
- Separate compliance rules

❌ **GRU → W Tokens**: Prohibited
- W tokens explicitly isolated from GRU
- No GRU conversion allowed

❌ **W Tokens → Credit Multiplier**: Prohibited
- W tokens must maintain m = 1.0
- No fractional reserve allowed

## Resolution

This architecture decision unblocks:
- INT-ISO-001: Relationship clarified - SEPARATE systems
- INT-ISO-002: Compliance integration - Optional, can use eMoney ComplianceRegistry
- INT-CROSS-001: W tokens as collateral - ALLOWED, to be implemented
- BRG integrations: Both systems can bridge independently

**Status**: ✅ ARCHITECTURE DECISION COMPLETE - All integrations can proceed
