# Systems Perspective Description Language — Maritime Navigation (SPDL-NAV)
**Specification Document ID:** `SPDL-NAV-SPEC-2026-v4.2`  
**Classification:** Open Epistemic Standard / Real-Time Zero-Heap Marine Autonomous Substrate  
**Principal Architect:** Asse van Nix | Systems Perspective Framework & Proof-Driven Architecture Group  
**Target Environment:** Zig 0.16.0 Freestanding · Marine Autopilot ECDIS Compute · NMEA 0183/2000 Replacement  
**Applied Standards:** ISO/IEC 14977 EBNF · GBNF Maskable · IMO COLREGs 1972 · IEC 61162 (NMEA 0183/2000 Replacement) · IMO Resolution MSC.252(83)  

---

## 1. Epistemic Architecture: Why NMEA 0183 and NMEA 2000 Must Be Replaced

1. **NMEA 0183 Text Frailty:** Uses unverified comma-separated ASCII sentences (`$GPRMC,...`) lacking structural types, units, and integrity guarantees.
2. **NMEA 2000 Proprietary Obscurity:** Cloaked behind paywalls and proprietary CAN PGN bit-packing. It has zero formal integration with the International Regulations for Preventing Collisions at Sea (COLREGs) or dynamic hydrodynamic ship stability margins.

**SPDL-NAV** directly unifies vessel hydrodynamics with COLREGs safety barrier certificates.

---

## 2. Physical Invariants, DAEs & Mathematical Proof Gates

```
                           SPDL-NAV HYDRODYNAMIC MANIFOLD
 ┌─────────────────────────────────────────────────────────────────────────────┐
 │ NON-LINEAR SHIP MANEUVERING DYNAMICS (Norrbin / Abkowitz Model)             │
 │   m * (u_dot - v * r - x_G * r^2) = X_hydro + X_prop                        │
 ├─────────────────────────────────────────────────────────────────────────────┤
 │ COLREGs RULE 13/14/15 STAND-ON & GIVE-WAY CONE BARRIER                      │
 │   h_colregs(p_own, p_target, DCPA, TCPA) = DCPA - DCPA_safe >= 0            │
 ├─────────────────────────────────────────────────────────────────────────────┤
 │ TRANSVERSE HYDRODYNAMIC INTACT STABILITY BARRIER (IMO A.749)                │
 │   h_stability(GM) = GM_actual - GM_minimum_allowable >= 0                   │
 └─────────────────────────────────────────────────────────────────────────────┘
```

---

## 3. Formal ISO/IEC 14977 EBNF Grammar

```ebnf
NavManifest       = { Line } ;
Line              = [ Whitespace ] , ( Comment | NavRecord ) , Newline ;
Whitespace        = { " " | "\t" | "\r" } ;
Newline           = "\n" | "\r\n" ;
Comment           = "#" , { AnyChar - Newline } ;

NavRecord         = "(I) @NAV_INVARIANT"     , " " , InvariantFields
                  | "(M) @VESSEL_HYDRO"      , " " , HydroFields
                  | "(B) @COLREGS_BARRIER"   , " " , ColregsFields
                  | "(B) @STABILITY_BARRIER" , " " , StabilityFields
                  | "(M) @AUTOPILOT_CMD"     , " " , AutopilotFields
                  | "(T) @NAV_OBSERVER"      , " " , ObserverFields ;

InvariantFields   = "id:" , Token , " mmsi:" , Integer , " imo_class:MASS_DEGREE_4" , " alloc_policy:ZERO_HEAP" ;
HydroFields       = "id:" , Token , " length_m:" , Number , " beam_m:" , Number , " draft_m:" , Number ;

ColregsFields     = "id:" , Token , " target_mmsi:" , Integer , " rule:" , ColregRule , " min_dcpa_nm:" , Number , " min_tcpa_min:" , Number ;
ColregRule        = "HEAD_ON_RULE14" | "CROSSING_GIVE_WAY_RULE15" | "OVERTAKING_RULE13" ;
StabilityFields   = "id:" , Token , " min_gm_m:" , Number , " max_heel_deg:" , Number ;

AutopilotFields   = "id:" , Token , " rudder_cmd_deg:" , Number , " engine_rpm:" , Integer , " heading_set_deg:" , Number ;
ObserverFields    = "id:" , Token , " sog_knots:" , Number , " cog_deg:" , Number , " rot_deg_min:" , Number , " depth_m:" , Number ;

Token             = Letter , { Letter | Digit | "_" | "-" } ;
Number            = [ "-" ] , Digit , { Digit } , [ "." , { Digit } ] ;
Integer           = [ "-" ] , Digit , { Digit } ;
Letter            = "A".."Z" | "a".."z" ;
Digit             = "0".."9" ;
AnyChar           = ? Any valid Unicode code point ? ;
```

---

## 4. GBNF Structured Sampling Grammar

```gbnf
root ::= NavRecord "\n"

NavRecord ::= "(I) @NAV_INVARIANT" " " InvariantFields
            | "(M) @VESSEL_HYDRO" " " HydroFields
            | "(B) @COLREGS_BARRIER" " " ColregsFields
            | "(B) @STABILITY_BARRIER" " " StabilityFields
            | "(M) @AUTOPILOT_CMD" " " AutopilotFields
            | "(T) @NAV_OBSERVER" " " ObserverFields

InvariantFields ::= "id:" [A-Za-z0-9_-]+ " mmsi:" [0-9]+ " imo_class:MASS_DEGREE_4 alloc_policy:ZERO_HEAP"
HydroFields     ::= "id:" [A-Za-z0-9_-]+ " length_m:" [0-9.]+ " beam_m:" [0-9.]+ " draft_m:" [0-9.]+
ColregsFields   ::= "id:" [A-Za-z0-9_-]+ " target_mmsi:" [0-9]+ " rule:" ("HEAD_ON_RULE14"|"CROSSING_GIVE_WAY_RULE15"|"OVERTAKING_RULE13") " min_dcpa_nm:" [0-9.]+ " min_tcpa_min:" [0-9.]+
StabilityFields ::= "id:" [A-Za-z0-9_-]+ " min_gm_m:" [0-9.]+ " max_heel_deg:" [0-9.]+
AutopilotFields ::= "id:" [A-Za-z0-9_-]+ " rudder_cmd_deg:" [0-9.-]+ " engine_rpm:" [0-9]+ " heading_set_deg:" [0-9.]+
ObserverFields  ::= "id:" [A-Za-z0-9_-]+ " sog_knots:" [0-9.]+ " cog_deg:" [0-9.]+ " rot_deg_min:" [0-9.-]+ " depth_m:" [0-9.]+
```

---

## 5. Production SPDL-NAV Manifest Exemplar

```spdl
# ==============================================================================
# SPDL-NAV v4.2 MANIFEST: AUTONOMOUS CONTAINER VESSEL (IMO MASS DEGREE 4)
# Standard: IMO COLREGs 1972 | Engine: Freestanding Zero-Heap Navigation Substrate
# ==============================================================================

(I) @NAV_INVARIANT id:INV-NAV-CORE mmsi:244010200 imo_class:MASS_DEGREE_4 alloc_policy:ZERO_HEAP

# --- SHIP HYDRODYNAMIC ASSETS ---
(M) @VESSEL_HYDRO id:HULL_CONTAINER_140M length_m:142.5 beam_m:24.2 draft_m:7.8

# --- COLREGs SPATIAL & SHIP ROLL BARRIERS ---
(B) @COLREGS_BARRIER id:BAR_COLREG_CROSSING target_mmsi:211345000 rule:CROSSING_GIVE_WAY_RULE15 min_dcpa_nm:1.5 min_tcpa_min:12.0
(B) @STABILITY_BARRIER id:BAR_INTACT_STABILITY min_gm_m:0.85 max_heel_deg:10.0

# --- AUTOPILOT STEERING COMMANDS ---
(M) @AUTOPILOT_CMD id:CMD_TRACK_HOLD rudder_cmd_deg:-4.2 engine_rpm:115 heading_set_deg:042.5

# --- BRIDGE TELEMETRY (REPLACING NMEA 0183/2000) ---
(T) @NAV_OBSERVER id:TEL_PRIMARY_NAV sog_knots:18.4 cog_deg:042.8 rot_deg_min:-0.5 depth_m:42.0
```

---

## 6. Standards Compliance Matrix

```
╔═════════════════════════════════╦══════════════════════╦═════════════════════════════════════════════════════╗
║ Dimension                       │ Verification Standard│ Enforced Implementation Evidence                    ║
╠═════════════════════════════════╬══════════════════════╬═════════════════════════════════════════════════════╣
║ Collision Regulations           │ IMO COLREGs 1972     │ DCPA/TCPA distance barrier prevents close-quarters. ║
║ Hydrodynamic Vessel Stability   │ IMO Resolution A.749 │ Intact GM >= 0.85m enforced prior to rudder exec.   ║
║ Marine Sensor Serialization     │ IEC 61162 Replacement│ Replaces brittle ASCII sentences with zero-heap AST.║
║ Autonomous Shipping Control     │ IMO MASS Degree 4    │ Deterministic autonomous maneuvering on silicon.    ║
╚═════════════════════════════════╩══════════════════════╩═════════════════════════════════════════════════════╝
```