Entity types

Entity types describe items in the data model, such as assets, equipment, locations, or systems. They are defined in Schema messages as type definitions.

You can define an entity by setting the classification to entity. Defining an entity type does not create any data by itself, it describes what an entity looks like, what properties it has, and how it can relate to other types.

Entity types usually:

• Represent objects that exist independently of time-series data

• Include one or more indexed properties to uniquely identify each entity

• Hold descriptive information such as names, tags, or metadata

• Act as the anchor point for related streaming data and events

After defining an entity type in the schema, create the actual entities at runtime using Instance messages. Entity instances are sent in the Entities array, along with their property values. Any relationships involving entities, such as asset hierarchies or links to measurements, must follow the relationship patterns defined in the schema.

Entity type examples

The following examples demonstrate how entity types are defined to model assets, equipment, locations, and other business objects.

Entity type definition

The following example for a cylindrical storage tank illustrates a single entity and how its properties describe a physical asset:

{

"types": [

{

"id": "CylindricalTank",

"classification": "entity",

"properties": {

"Serial": { "type": "string" },

"Model": { "type": "string" },

"TankDiameter": { "type": "number" },

"TankHeight": { "type": "number" },

"Inventory": {

"reftypeid": "InventoryInfo"

}

}

}

}

Entity components

The following example defines two component types and applies both components to one entity.

omfversion: 2.0

messagetype: schema

action: create

messageformat: json

{

"types": [

{

"id": "TankAsset",

"version": "1.0.0",

"type": "object",

"classification": "entity",

"properties": {

"SerialNumber": {

"type": "string"

},

"Model": {

"type": "string"

},

"Capacity": {

"type": "number",

"format": "float64",

"uom": "m3"

}

}

},

{

"id": "InventoryRecord",

"version": "1.0.0",

"type": "object",

"classification": "entity",

"properties": {

"InventoryNumber": {

"type": "string"

},

"Manufacturer": {

"type": "string"

},

"ManufactureDate": {

"type": "string",

"format": "date"

}

}

}

]

}