{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://raw.githubusercontent.com/api-evangelist/aspentech/refs/heads/main/json-schema/aspentech-dataitem-schema.json",
  "title": "AspenTech Inmation Data Item",
  "description": "JSON Schema for an AspenTech Inmation process data item (tag) including current value, quality, and historical data.",
  "type": "object",
  "required": ["path"],
  "properties": {
    "path": {
      "type": "string",
      "description": "Full hierarchical path to the data item in the Inmation system tree (e.g., /System/Core/Plant1/Temperature)"
    },
    "value": {
      "description": "Current process value - can be numeric, string, or boolean",
      "oneOf": [
        {"type": "number"},
        {"type": "string"},
        {"type": "boolean"},
        {"type": "null"}
      ]
    },
    "quality": {
      "type": "integer",
      "description": "OPC UA/DA quality code (192=Good, 0=Bad, 64=Uncertain)",
      "minimum": 0,
      "maximum": 255
    },
    "timestamp": {
      "type": "string",
      "format": "date-time",
      "description": "Timestamp of the current value (ISO 8601 UTC)"
    },
    "engineeringUnit": {
      "type": "string",
      "description": "Engineering unit for the value (e.g., degC, bar, m3/h)"
    },
    "itemType": {
      "type": "string",
      "description": "Type of Inmation item",
      "enum": ["GenItem", "InmationGenItem", "Model", "Trend", "Calculation", "Connector"]
    },
    "name": {
      "type": "string",
      "description": "Item display name"
    },
    "description": {
      "type": "string",
      "description": "Item description"
    },
    "highLimit": {
      "type": "number",
      "description": "High engineering range limit"
    },
    "lowLimit": {
      "type": "number",
      "description": "Low engineering range limit"
    },
    "alarmHigh": {
      "type": "number",
      "description": "High alarm threshold"
    },
    "alarmLow": {
      "type": "number",
      "description": "Low alarm threshold"
    },
    "deadband": {
      "type": "number",
      "description": "Deadband for value change detection",
      "minimum": 0
    }
  },
  "$defs": {
    "HistoricalValue": {
      "type": "object",
      "required": ["value", "timestamp"],
      "properties": {
        "value": {
          "oneOf": [
            {"type": "number"},
            {"type": "string"},
            {"type": "boolean"},
            {"type": "null"}
          ]
        },
        "quality": {
          "type": "integer",
          "minimum": 0,
          "maximum": 255
        },
        "timestamp": {
          "type": "string",
          "format": "date-time"
        }
      }
    }
  }
}