chore: remove unneeded second level of "media"

Figure C.2.1-1 shows a diagram representing a property graph to be used for the examples discussed in this clause.

![](media/media/image143.png)

![](media/image143.png)

**Figure C.2.1-1: Reference example**

- Additional NGSI-LD Properties the NGSI-LD system has to have, in order to represent and manage command Request, Status, Result.

- A communication model that allows commands to flow in forward direction and feedback to flow in reverse. This communication model has to comprise a mapping, to be held within the NGSI-LD system, that is able to route the command requests to the appropriate handler within the Context Adapter and vice-versa.

![](media/media/image144.png)

![](media/image144.png)

**Figure H.2-1: Architecture for actuation**

7.  Context Adapter updates [turn-on-RESULT]{.HTML-Variable} command Property with ["value": "OK"]{.HTML-Code}

8.  Application gets notification with of the new value ["OK"]{.HTML-Code}

![](media/media/image145.png)

![](media/image145.png)

**Figure H.4.2-1: Steps of the actuation workflow using subscription/notification**

8.  Context Adapter updates[turn-on-RESULT]{.HTML-Variable}["value": "OK"]{.HTML-Code}

9.  Application gets notification with of the new value["OK"]{.HTML-Code}

![](media/media/image146.png)

![](media/image146.png)

**Figure H.4.3-1: Steps of the actuation workflow using forwarding**

In Figure H.5-1 a diagram shows how VirIoT implements the concept of a large-scale and distribute NGSI-LD system that leverages the architecture and the workflow convention described in clause H.4.2.

![](media/media/image147.png)

![](media/image147.png)

**Figure H.5-1: VirIoT implementation of the NGSI-LD system and actuation workflow**

- Requests between IoT Device and IoT Agent use native protocols

- Requests between IoT Agent and [Context Broker]{.HTML-Keyboard} use NGSI-LD

![](media/media/image148.png)

![](media/image148.png)

**Figure H.6-1: IoT Agent node library implementation of the NGSI-LD system and actuation workflow**

The version of the cross-domain model proposed by the present document is a minimal one, aimed at defining the classes used in this release of the API specification. It has been extended by other work items like ETSI GS CIM 006 [i.8], with classes defining extra concepts such as mobile vs. stationary entities, instantaneous vs. static properties, etc.

![](media/media/image2.png)

![](media/image2.png)

**Figure 4.2.1-1: Overview of the NGSI-LD Information Model Structure**

Figure 4.2.2-1 provides a graphical representation of the NGSI-LD Meta-Model in terms of classes and their relationships. To provide additional clarity an informal (non-normative) mapping to the Property Graph Model is also presented.

![](media/media/image3.png)

![](media/image3.png)

::: NF

Legend:

+-------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| {NF}                                                        | {NF}                                                                                                                                                                                                                                                                 |

|                                                             |                                                                                                                                                                                                                                                                      |

| ![](media/media/image4.png)                                 | [With capital initial]. Used to refer to a class that is a subclass of Entity or Value.                                                                                                                                                                              |

| ![](media/image4.png)                                 | [With capital initial]. Used to refer to a class that is a subclass of Entity or Value.                                                                                                                                                                              |

+=============================================================+======================================================================================================================================================================================================================================================================+

| ![](media/media/image5.png)                                 | [With capital initial]. Used to refer to a class that is a subclass of Property or Relationship, but which is not itself a property or a relationship. These classes serve as super-classes for a set of properties or relationships in the same domain or aspect.   |

| ![](media/image5.png)                                 | [With capital initial]. Used to refer to a class that is a subclass of Property or Relationship, but which is not itself a property or a relationship. These classes serve as super-classes for a set of properties or relationships in the same domain or aspect.   |

+-------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| ![](media/media/image6.png) and ![](media/media/image7.png) | [With small initial]. Used to refer to a proper (direct) class of properties or relationships.                                                                                                                                                                       |

| ![](media/image6.png) and ![](media/image7.png) | [With small initial]. Used to refer to a proper (direct) class of properties or relationships.                                                                                                                                                                       |

+-------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| ![](media/media/image8.png)                                 | [With small initial and underlined text]. Used to refer to the name of a property that is considered to be "lite" in its informational representation since it shall not be reified, rather a value is directly attached to it.                                      |

| ![](media/image8.png)                                 | [With small initial and underlined text]. Used to refer to the name of a property that is considered to be "lite" in its informational representation since it shall not be reified, rather a value is directly attached to it.                                      |

+-------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| ![](media/media/image9.png)                                 | [With small or capital initial]. Used to refer to a class or a vocabulary that is inherited from another publicly available standard or ontology.                                                                                                                    |

| ![](media/image9.png)                                 | [With small or capital initial]. Used to refer to a class or a vocabulary that is inherited from another publicly available standard or ontology.                                                                                                                    |

+-------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

<!-- prettier-ignore-end -->

:::

### 4.2.3 Cross Domain Ontology

![](media/media/image10.png)

![](media/image10.png)

::: NF

Legend:

+------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| {NF}                                                       | {NF}                                                                                                                                                                                                                                                                 |

|                                                            |                                                                                                                                                                                                                                                                      |

| ![](media/media/image4.png)                                | [With capital initial]. Used to refer to a class that is a subclass of Entity or Value.                                                                                                                                                                              |

| ![](media/image4.png)                                | [With capital initial]. Used to refer to a class that is a subclass of Entity or Value.                                                                                                                                                                              |

+============================================================+======================================================================================================================================================================================================================================================================+

| ![](media/media/image5.png)                                | [With capital initial]. Used to refer to a class that is a subclass of Property or Relationship, but which is not itself a property or a relationship. These classes serve as super-classes for a set of properties or relationships in the same domain or aspect.   |

| ![](media/image5.png)                                | [With capital initial]. Used to refer to a class that is a subclass of Property or Relationship, but which is not itself a property or a relationship. These classes serve as super-classes for a set of properties or relationships in the same domain or aspect.   |

+------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| ![](media/media/image6.png)and ![](media/media/image7.png) | [With small initial]. Used to refer to a proper (direct) class of properties or relationships.                                                                                                                                                                       |

| ![](media/image6.png)and ![](media/image7.png) | [With small initial]. Used to refer to a proper (direct) class of properties or relationships.                                                                                                                                                                       |

+------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| ![](media/media/image8.png)                                | [With small initial and underlined text]. Used to refer to the name of a property that is considered to be "lite" in its informational representation since it shall not be reified, rather a value is directly attached to it.                                      |

| ![](media/image8.png)                                | [With small initial and underlined text]. Used to refer to the name of a property that is considered to be "lite" in its informational representation since it shall not be reified, rather a value is directly attached to it.                                      |

+------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

| ![](media/media/image9.png)                                | [With small or capital initial]. Used to refer to a class or a vocabulary that is inherited from another publicly available standard or ontology.                                                                                                                    |

| ![](media/image9.png)                                | [With small or capital initial]. Used to refer to a class or a vocabulary that is inherited from another publicly available standard or ontology.                                                                                                                    |

+------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

<!-- prettier-ignore-end -->

:::

Figure 4.2.4-1 shows an example of an NGSI-LD domain-specific model. Domain-specific models introduce the specific entity types required for a particular domain. Figure 4.2.4-1 shows the types ["Car"]{.HTML-Code}, ["Parking"]{.HTML-Code}, ["Street"]{.HTML-Code}, ["Gate"]{.HTML-Code}. Entity types can have further subtypes, e.g. ["OffStreetParking"]{.HTML-Code} as subtype of ["Parking"]{.HTML-Code}.

![](media/media/image11.png)

![](media/image11.png)

**Figure 4.2.4-1: Cross-Domain Ontology and instantiation**

In Figure 4.2.5-1 NGSI-LD Entity, Relationship, Property and Value are represented as UML classes. UML associations are used to interrelate these classes while keeping the structure and semantics defined by the NGSI-LD Information Model.

![](media/media/image12.png)

![](media/image12.png)

**Figure 4.2.5-1: NGSI-LD information model as UML**

Figure 4.3.2-1 shows a centralized architecture. In the centre is a [Central Broker]{.HTML-Keyboard} that stores all the context information. There are [Context Producers]{.HTML-Keyboard} that use update operations to update the context information in the [Central Broker]{.HTML-Keyboard} and there are [Context Consumers]{.HTML-Keyboard} that request context information from the [Central Broker]{.HTML-Keyboard}, either using synchronous one-time query or asynchronous subscribe/notify operations. The [Central Broker]{.HTML-Keyboard} answers all requests from its storage. Figure 4.3.2-1 shows one component that acts as both [Context Producer]{.HTML-Keyboard} and [Context Consumer]{.HTML-Keyboard}. The general assumption is that components can have multiple roles, so such components are not explicitly shown in clauses 4.3.3 and 4.3.4.

![](media/media/image13.png)

![](media/image13.png)

**Figure 4.3.2-1: Centralized architecture**

Figure 4.3.3-1 shows a distributed architecture. The underlying idea here is that all information is stored by the [Context Sources]{.HTML-Keyboard}. [Context Sources]{.HTML-Keyboard} implement the query and subscription part of the NGSI-LD API as a [Context Broker]{.HTML-Keyboard} does. They register themselves with the [Context Registry]{.HTML-Keyboard}, providing information about what context information they can provide, but not the context information itself, e.g. a certain [Context Source]{.HTML-Keyboard} registers that it can provide the indoor temperature for Building A and Building B or that it can provide the speed of cars in a geographic region covering the centre of a city.

![](media/media/image14.png)

![](media/image14.png)

**Figure 4.3.3-1: Distributed architecture**

The federated architecture shown in Figure 4.3.4-1 is used in cases where existing domains are to be federated. For example, different departments in a city operate their own [Context Broker]{.HTML-Keyboard}-based NGSI-LD infrastructure, but applications should be able to easily access all available information using just one point of access. The architecture works in the same way as the distributed architecture described in clause 4.3.3, except that instead of simple [Context Sources]{.HTML-Keyboard}, whole domains are registered with the respective [Context Broker]{.HTML-Keyboard} as point of access. Typically, the domains will be registered to the federation [Context Registry]{.HTML-Keyboard} on a more coarse-grained level, providing scopes, in particular geographic scopes, that can then be matched to the scopes provided in the requests. For example, instead of registering individual entities like buildings, the domain would be registered with having information about entities of type building within a geographic area. Applications then query or subscribe for entities within a geographic scope, e.g. buildings in a certain area of the city. The [Federation Broker]{.HTML-Keyboard} discovers the domain [Context Brokers]{.HTML-Keyboard} that can provide relevant information, forwards the request to these [Context Brokers]{.HTML-Keyboard} and aggregates the results, so the application gets the result in the same way as in the centralized and distributed cases.

![](media/media/image15.png)

![](media/image15.png)

**Figure 4.3.4-1: Federated architecture**