## 5 Sensors, Actuators and External Services Integration  
At the northbound interface, CAMINO-Core is integrated with the DUST framework [13] using publisher/subscriber architecture. DUST optimizes the distribution of resources in a modern IoT environment. The core of the DUST framework, called DUST-Core, allows different application components to stream events between each other by using DUST messages. As the components should be able to migrate between devices, the underlying middleware configuration must be interchangeable. As such, the DUST-Core makes an abstraction of this towards the application components. Currently, MQTT, ZeroMQ and Data Distribution Service messaging protocols are supported by DUST. To integrate the DUST framework in the CAMINO framework, we have developed a series of publishers that can be used to trigger specific services at CAMINO-Core based on information that may derive from the CAN BUS or the sensors of the vehicle/Road-Side Unit (RSU) and a series of subscribers that bring the information from the different ITS services in the vehicle/RSU. This information may be used to trigger an actuator (e.g., towards autonomous driving) or to be visualized using an HMI. The DUST enabled applications can run on the same computing unit as the CAMINO-Core but can also be distributed to other processing units. The capabilities of the CAMINO framework to dynamically trigger services, communicate with the environment (e.g., sensors) and bring information in the vehicle (actuators, HMIs) can enable several C-ITS use cases such as Road Hazard Warning (RHW), In-Vehicle Signage (IVS), Electronic Emergency Brake Light (EEBL) and many more. In order to trig \begin{table}
\begin{tabular}{c c} \hline \hline
**C-ITS Application** & **Version** \\ \hline CAM & ETSI EN 302 637-2 V1.4.1 and ETSI EN 302 637-2 V1.3.2 \\ DENM & ETSI EN 302 637-3 V1.3.1 and ETSI EN 302 637-3 V1.2.2 \\ IVIM & ETSI TS 103 301, version 1, 2016, ISO/TS 19321:2015 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Supported Cooperative Intelligent Transport Systems (C-ITS) application specifications. ger DENM and IVIM messages that can enable such use cases, the CAMINO framework provides implementations of related DUST publisher and subscribers. For instance, regarding the RHW or the EEBL, the developed DUST publishers can trigger the transmission of DENM messages for a series of virtual or real hazardous situations that are identified by the sensors of the vehicle, such as a slow or stationary vehicle, roadworks, brake event, etc. On the other hand, when the CAMINO-Core instance of a vehicle receives a DENM message through a V2X wireless technology, it decodes it and publishes the relevant information to the developed DUST DENM subscriber. The DUST subscriber of the DENM messages, receives this information, and according to the considered scenario, it either depicts a warning to the driver of the vehicle or triggers a relevant actuator (e.g., slowing down the vehicle). As an example, an EEBL demo was implemented, where a brake event at the vehicle was detected by reading out CAN BUS data from the brake pedal. When the pressure on the brake pedal exceeded a certain threshold, an event message was generated and sent to the CAMINO via the DUST-Core. The CAMINO-Core was then able to transmit this event message using a DENM over the different V2X technologies [19]. For the IVS use case, we have developed a DUST publisher that gives vehicles real-time access to the information on the electronic traffic signs located on top of the gantries along the Belgian highways. To this end, we have developed an application that periodically fetches the traffic sign values from the public datasets provided by the Belgian Government and thus acts as an external third party service provider. Based on the desired configuration parameters, the DUST publisher filters out the data and creates a JSON message that includes all the relevant information, such as the traffic sign per lane, the coordinates of the gantry, the timestamp when each sign was updated, etc.