# The Architecture of an Agricultural Data Aggregation and Conversion Model for Smart Farming
## 2 Review
The semantic middleware offers the following components: data storage and retrieval in the cloud; image management and cataloguing; the on-farm registration of IoT devices, animals, and vehicles; the management of data flows within the platform; the management of ground and unmanned vehicles; and the processing of the resulting data [18; 19; 20]. Semantic middleware installs the software so that the farm management system can access the devices in a unified way. The semantic middleware acts as a communicationcentraliser, distributing messages between the farm management system and the devices. Semantic middleware offers a set of device-level communication interfaces. For example, a decision support system to send tasks to ground and unmanned vehicles and receive real-time feedback and status; ISOBUS to manage communications with ISOBUS-compatible ground vehicles; MQTT to manage communications with individual and onboard sensors and actuators; and REST to retrieve data from legacy system databases [14]. The equipment layer enables the installation and integration of services and data related to unmanned aerial vehicles, ground vehicles, actuators, sensors, and other connectivity devices. In this complex context, extensive sensor testing is required before prototypes can be deployed in the field [21]. The different formats of the hardware applications of farm machinery make it difficult for farmers to engage and develop precision agriculture [22]. The possible communication between the different intelligent farm management applications is also not standardised. The standardisation of the transmission of data between machines and implements began with the formats AgroXML and AgXML. Unification is necessary for communication protocols and data processing; moreover, it is also essential to pay attention to the level of security, the amount of time required to process the data, and the overall costs [23]. A standardised interface evolved through the gradual development of individual systems, including a binary data format and CAN (_Controller Area Network_)-protocol-type communication [24]. The CAN bus and the data transfer protocols had to be modified from closed-to open-type for interchangeable devices. The expanded information was embedded in the data transfer protocol according to eight priority groups depending on the significance of the data object. The so-called ISO-XML format, defined by the international standard ISO 11783 [25], is used for data transmission in agricultural machinery. This standardised data interface was first introduced using a standardised connector between a tractor and a connected implement [26]. The interface has been developed into a CAN-type 250 kbps data bus to which other agricultural peripherals and tractor control computers are connected [27]. ISO 11783 provides a network of embedded software for data transmission between sensors, controllers, and control devices, both on the tractor and connected implements. The standard also defines a protocol for transmitting data to data servers (cloud storage) and later via mobile devices. A designated computer, usually located in the driver's cab, collects all the data, which is then exported via USB, another interface, or wirelessly for further use in increasingly used systems such as farm management information systems (FMISs) [10]. Wireless data transmission is associated with telematics systems in which the data can already be converted into the required format. The following companies already offer commercial telematics services: AGCO (AgCommand) (owned by _Challenger, Fendt, Massey Ferguson, and Valtra Farm_), _John Deere_ (system JDLink), _Claas Telematics_, Raven Slingshot, and Trimble Connected Farm [28]. Using an XML (_extensible markup language_) data format, the protocol implements real-time data transmission, such as between a machine and an FMIS [28; 29]. This is achieved using a simple in-cab device, the task controller, which records and/or manages data transmitted via a standardised protocol.