# 📐  L2 Spec — System Identification (N4SID/ARX) — Nominal + Mismatch Specs

**ID:** `L2-431-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-431`](/artifact/l1/L1-431)

> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.28 · **Delta tier:** 5
> **⛓ On-chain block:** 41555243

---

## 1. Domain Ω

**Type:** `range`

| Parameter | Unit | Range |
|---|---|---|
| Input snr db | dB | 10 – 60 |
| N data points | — | 100 – 100000 |
| Model order n | N | 1 – 20 |
| Bandwidth fraction | — | 0.1 – 0.9 |

## 2. Tolerance (ε)

**Type:** `fn`

```
70 + 15 * (N_data_points / 1000) ** 0.2
```

## 3. Difficulty

| Property | Value |
|---|---|
| Difficulty score | 0.28 |
| Delta tier | 5 |

## 4. Fingerprint

`8b6e185e483302b388a4235b36078cda08526e6f401702f11c352923e8d98d2f`

## 5. On-chain Registration

- **Chain hash:** `0xca1c27aa018e6f5046c18587df1c96b7b133e289d7e7819663b59f4d89c992c2`
- **Chain tx hash:** `0x84cc084bc37be57776c1ddb73c19065b92d7568c60f1c0c84a875cd050af24b3`
- **Chain block:** `41555243`

---

## File Mapping

This bundle consists of: `L2-431-001.md`, `L2-431-001.json`.

| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-431-001.md` | Source of truth — edit this | Human or LLM |
| `L2-431-001.json` | Structured metadata for the registry | LLM regenerates from the sections above |

**Prompt for your LLM after editing this Markdown:**

> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.

_This Markdown was auto-synthesized from the catalog row for `L2-431-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._