設序列化綱

立善版之序綱，演進而不破用者。

用

• 立新 API 契或數換格
• 舊綱添欄而不破用者
• 於綱版間遷
• 擇綱系（JSON Schema、Protobuf、Avro）
• 書數驗規以動施

入

• 必：數模（實體關、欄類、限）
• 必：相容求（誰用此數、舊格宜可讀多久）
• 可：可演之舊綱
• 可：效求（驗速、綱註冊表整合）
• 可：目序格（JSON、二進、列式）

行

一：擇綱系

得：綱系依生態、效需、演求擇。

敗：不定→始 JSON Schema—工具支援最廣，可疊於舊 JSON API。

二：設核綱

JSON Schema 例：

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://example.com/schemas/measurement/v1",
  "title": "Measurement",
  "description": "A sensor measurement reading",
  "type": "object",
  "required": ["sensor_id", "value", "unit", "timestamp"],
  "properties": {
    "sensor_id": {
      "type": "string",
      "pattern": "^[a-z]+-[0-9]+$",
      "description": "Unique sensor identifier (lowercase-digits format)"
    },
    "value": {
      "type": "number",
      "description": "Measured value"
    },
    "unit": {
      "type": "string",
      "enum": ["celsius", "fahrenheit", "kelvin", "percent", "ppm"],
      "description": "Unit of measurement"
    },
    "timestamp": {
      "type": "string",
      "format": "date-time",
      "description": "ISO 8601 timestamp with timezone"
    },
    "metadata": {
      "type": "object",
      "additionalProperties": true,
      "description": "Optional key-value metadata"
    }
  },
  "additionalProperties": false
}

Protocol Buffers 例：

syntax = "proto3";
package sensors.v1;

import "google/protobuf/timestamp.proto";

// Measurement represents a single sensor reading.
message Measurement {
  string sensor_id = 1;         // Unique sensor identifier
  double value = 2;             // Measured value
  Unit unit = 3;                // Unit of measurement
  google.protobuf.Timestamp timestamp = 4;
  map<string, string> metadata = 5; // Optional key-value metadata
}

enum Unit {
  UNIT_UNSPECIFIED = 0;
  UNIT_CELSIUS = 1;
  UNIT_FAHRENHEIT = 2;
  UNIT_KELVIN = 3;
  UNIT_PERCENT = 4;
  UNIT_PPM = 5;
}

Apache Avro 例：

{
  "type": "record",
  "name": "Measurement",
  "namespace": "com.example.sensors",
  "doc": "A sensor measurement reading",
  "fields": [
    {"name": "sensor_id", "type": "string", "doc": "Unique sensor identifier"},
    {"name": "value", "type": "double", "doc": "Measured value"},
    {"name": "unit", "type": {"type": "enum", "name": "Unit", "symbols": ["CELSIUS", "FAHRENHEIT", "KELVIN", "PERCENT", "PPM"]}},
    {"name": "timestamp", "type": {"type": "long", "logicalType": "timestamp-millis"}},
    {"name": "metadata", "type": ["null", {"type": "map", "values": "string"}], "default": null}
  ]
}

得：綱自書，含述、限、明類定。

敗：數模未穩→標綱為 draft 勿發於註冊表。

三：備綱演

相容規：

安演策：

1. 僅添可選欄含合理默認
2. 永勿去或改名—宜棄用
3. 於識中版綱（v1、v2）
4. 用綱註冊表於二進格（Confluent Schema Registry 於 Avro/Protobuf）

Protobuf 演規：

// v1 — original
message Measurement {
  string sensor_id = 1;
  double value = 2;
  Unit unit = 3;
}

// v2 — safe evolution
message Measurement {
  string sensor_id = 1;
  double value = 2;
  Unit unit = 3;
  // NEW: added in v2 — old clients ignore this field
  google.protobuf.Timestamp timestamp = 4;
  // DEPRECATED: use sensor_id instead
  reserved 6;
  reserved "old_sensor_name";
}

JSON Schema 版：

{
  "$id": "https://example.com/schemas/measurement/v2",
  "allOf": [
    {"$ref": "https://example.com/schemas/measurement/v1"},
    {
      "properties": {
        "location": {
          "type": "string",
          "description": "Added in v2: GPS coordinates"
        }
      }
    }
  ]
}

得：演計已書：何變安、何需新版。

敗：破變不可免→版綱（v1 → v2）並於遷間維並行支援。

四：施綱驗

# JSON Schema validation (Python)
from jsonschema import validate, ValidationError
import json

schema = json.load(open("measurement_v1.json"))

def validate_measurement(data: dict) -> list[str]:
    """Validate a measurement against the schema. Returns list of errors."""
    errors = []
    try:
        validate(instance=data, schema=schema)
    except ValidationError as e:
        errors.append(f"{e.json_path}: {e.message}")
    return errors

# Usage
errors = validate_measurement({"sensor_id": "s-01", "value": "not_a_number"})
# → ["$.value: 'not_a_number' is not of type 'number'"]

// TypeScript with Zod (runtime + compile-time)
import { z } from 'zod';

const MeasurementSchema = z.object({
  sensor_id: z.string().regex(/^[a-z]+-[0-9]+$/),
  value: z.number(),
  unit: z.enum(['celsius', 'fahrenheit', 'kelvin', 'percent', 'ppm']),
  timestamp: z.string().datetime(),
  metadata: z.record(z.string()).optional(),
});

type Measurement = z.infer<typeof MeasurementSchema>;

// Validation
const result = MeasurementSchema.safeParse(inputData);
if (!result.success) {
  console.error(result.error.issues);
}

得：驗行於系邊界諸入數（API 端、檔攝）。

敗：誌驗誤及全載（遮敏欄）以備除錯。

五：書綱

立綱書頁：

# Measurement Schema (v1)

## Overview
Represents a single sensor reading with metadata.

## Fields
| Field | Type | Required | Description | Constraints |
|-------|------|----------|-------------|-------------|
| sensor_id | string | Yes | Unique sensor ID | Pattern: `^[a-z]+-[0-9]+$` |
| value | number | Yes | Measured value | Any valid IEEE 754 double |
| unit | enum | Yes | Unit of measurement | One of: celsius, fahrenheit, kelvin, percent, ppm |
| timestamp | string | Yes | Reading time | ISO 8601 with timezone |
| metadata | object | No | Key-value pairs | String keys and values |

## Changelog
| Version | Date | Changes |
|---------|------|---------|
| v1 | 2025-03-01 | Initial schema |

## Compatibility
- **Backwards**: Consumers of v1 will continue to work with future versions
- **Policy**: Only additive, optional field changes between minor versions

得：書動生或與綱定同步。

敗：書漂離綱→加 CI 查以驗書對綱源。

驗

• 綱用案宜之系（JSON Schema、Protobuf、Avro）
• 諸欄有類、述、限
• 必 vs 可欄明定
• 演策已書（安變、版策）
• 系邊界已施驗
• 綱已版含變誌
• 往返測：序→反序→比確無數失

忌

• 過早過限：新綱嚴驗塞迭代→始寬（additionalProperties: true），後緊
• 無默值：添必欄而無默→破諸舊數→新欄常供默
• 略 null：多綱不明 null／缺欄→明 nullable vs optional
• 於負載版而非 URL：長壽數（存、事）→嵌綱版於數中，非僅端點 URL
• enum 窮舉：添新 enum 值可崩用窮舉 switch 之用者→書無知值宜優雅處

參

• serialize-data-formats
• implement-pharma-serialisation
• write-validation-documentation