Model: Entity Instance

An entity instance is an object with characteristics that is of a specific entity type. An entity instance contains a property instance for each property type defined either in the entity type or in one of the entity type's components.

In contrast to entity types, property instances are contained and each property instance contains a data stream and its last value.

UUIDs

Entity instances can be uniquely identified via a UUID. This is particularly important when entity instances are synchronized in a distributed system. For example, a player's representation exists not only in the local client, but also on the server and on clients connected to it.

Error rendering admonishment

Failed with: TOML parsing error: expected an equals, found an identifier at line 1 column 6

Original markdown input:

```admonish info UUIDs
* UUIDs are unique and unique across distributed systems
* UUIDs can be represented as string and as a 128 bit unsigned integer
```

Labels

Labels are also unique, but optional. While UUIDs are hard to remember, labels are easier to remember. This allows entity instances to be addressed using labels, for example in GraphQL queries.

If you compare the query with and without a label, you will find that the query is easier to understand thanks to the label and transports significantly more information about what is actually happening.

Info

Labels are optional

query {
  instances {
    entities(label: "/org/inexor/input/any_device/key/key_f7") {
      properties(name: "key_down") {
        value
      }
    }
  }
}

query {
  instances {
    entities(id: "c7ec76e0-40e8-587e-bc89-e9cd31fa75a0") {
      properties(name: "key_down") {
        value
      }
    }
  }
}

Data Model

FieldDataTypeDescription
TypeEntityTypeThe type of the entity instance
IDUUIDThe unique identifier of the entity instance
LabelString (optional)The label of the entity instance
DescriptionStringTextual description of the entity type
PropertiesVec<Property Instance>The properties of the entity instance
ComponentsVecThe currently applied components
BehavioursVecThe currently applied behaviours

Graph

graph LR;
    EI(Entity Instance);
    I1(Entity Instance)===>|"Relation Instance"|EI;
    I2(Entity Instance)===>|"Relation Instance"|EI;
    I3(Entity Instance)===>|"Relation Instance"|EI;
    EI===>|"Relation Instance"|O1(Entity Instance);
    EI===>|"Relation Instance"|O2(Entity Instance);
    EI===>|"Relation Instance"|O3(Entity Instance);

ER Diagram

erDiagram
    Entity-Type {
        string name
        string namespace
        string description
    }
    Entity-Instance {
        string id
        string label
        string description
    }
    Relation-Type {
        string name
        string instanceTypeName
        string namespace
        string description
    }
    Relation-Instance {
        string name
        string instanceTypeName
        string namespace
        string description
    }
    Property-Type {
        string name
        string description
        enum DataType
        enum SocketType
    }
    Property-Instance {
        string name
        JSON value
    }
    Entity-Instance ||--}o Property-Instance : stores
    Entity-Instance o{--}o Relation-Instance : outbound
    Entity-Instance o{--}o Relation-Instance : inbound
    Relation-Instance ||--}o Property-Instance : stores
    Relation-Instance o{--|| Relation-Type : is-a
    Property-Instance o{--|| Property-Type : is-a
    Entity-Instance o{--|| Entity-Type : is-a
    Entity-Type ||--}o Property-Type : defines
    Relation-Type ||--}o Property-Type : defines
    Entity-Type ||--}o Relation-Type : outbound
    Entity-Type ||--}o Relation-Type : inbound

GraphQL