{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://raw.githubusercontent.com/api-evangelist/scada/main/json-schema/scada-tag-schema.json",
  "title": "ScadaTag",
  "description": "Schema for a SCADA data tag representing a sensor reading, setpoint, or control variable",
  "type": "object",
  "properties": {
    "tagId": {
      "type": "string",
      "description": "Unique identifier for the tag in the SCADA system",
      "example": "PLANT1.AREA2.PV_101"
    },
    "tagName": {
      "type": "string",
      "description": "Human-readable name for the tag",
      "example": "Reactor Inlet Pressure"
    },
    "tagPath": {
      "type": "string",
      "description": "Hierarchical path to the tag in the SCADA tag browser",
      "example": "Plant/Area2/Reactor/PV_101"
    },
    "value": {
      "description": "Current value of the tag (type depends on dataType)",
      "example": 14.7
    },
    "dataType": {
      "type": "string",
      "description": "Data type of the tag value",
      "enum": ["Float", "Double", "Integer", "Boolean", "String", "DateTime"],
      "example": "Float"
    },
    "timestamp": {
      "type": "string",
      "format": "date-time",
      "description": "ISO 8601 timestamp of the tag reading",
      "example": "2026-05-02T14:30:00.000Z"
    },
    "quality": {
      "type": "string",
      "description": "OPC-UA quality code indicating data reliability",
      "enum": ["Good", "Uncertain", "Bad", "Stale"],
      "example": "Good"
    },
    "engineeringUnits": {
      "type": "string",
      "description": "Physical engineering units for the tag value",
      "example": "PSI"
    },
    "description": {
      "type": "string",
      "description": "Human-readable description of what the tag measures",
      "example": "Pressure at reactor inlet measured by differential pressure transmitter PV-101"
    },
    "alarmLimits": {
      "type": "object",
      "description": "Configured alarm threshold limits for the tag",
      "properties": {
        "highHigh": {
          "type": "number",
          "description": "High-High alarm setpoint (critical)"
        },
        "high": {
          "type": "number",
          "description": "High alarm setpoint (warning)"
        },
        "low": {
          "type": "number",
          "description": "Low alarm setpoint (warning)"
        },
        "lowLow": {
          "type": "number",
          "description": "Low-Low alarm setpoint (critical)"
        }
      }
    },
    "deviceSource": {
      "type": "object",
      "description": "Source field device information",
      "properties": {
        "deviceId": {
          "type": "string",
          "description": "Identifier of the PLC or RTU providing the tag"
        },
        "deviceType": {
          "type": "string",
          "description": "Type of source device",
          "enum": ["PLC", "RTU", "DCS", "IED", "Sensor", "Controller"]
        },
        "protocol": {
          "type": "string",
          "description": "Communication protocol used to read this tag",
          "enum": ["Modbus-TCP", "OPC-UA", "DNP3", "EtherNet/IP", "PROFINET", "BACnet", "MQTT"]
        }
      }
    },
    "processArea": {
      "type": "string",
      "description": "Logical process area or plant unit this tag belongs to",
      "example": "Reactor Section"
    }
  },
  "required": ["tagId", "value", "dataType", "timestamp", "quality"],
  "additionalProperties": false
}