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.

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.

query {
  instances {
    entities(label: "/io/reactive-graph/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

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 namespace
        string name
    }
    Entity-Instance {
        string id
        string label
    }
    Relation-Type {
        string namespace
        string name
    }
    Relation-Instance {
        string namespace
        string name
        string instanceId
    }
    Property-Type {
        string name
        enum DataType
        enum SocketType
        enum Mutability
    }
    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
    Relation-Type ||--}o Property-Type : defines
    Entity-Type ||--}o Relation-Type : outbound
    Entity-Type ||--}o Relation-Type : inbound
    Entity-Type ||--}o Property-Type : defines

GraphQL

JSON Schema