Reasons:

• To make it possible to pass data from multiple different nodes through a central node without it being constantly transformed and converted (because the central node might be configured to listen for certain values via filters for special cases/events, which makes a common semantics a reasonable solution to avoid the need for complex conversions and transformations of data before being passed to filters).
• Working with a standardised communication protocol is easier than having to implement multiple libraries for multiple standards in a system that accumulates data from multiple IoT source nodes.
• Easier data querying. One engine can be modelled for a certain type of data transport format (JSON for example, which is native for most NoSQL engines).
• The possibility of making IoT nodes analogous with virtual Internet service APIs (RESTful design), removing the need to distinguish between situations where one communicates with a virtual Web service or a physical IoT node over the network. The data request data to the target is of the same format and the data received in the response is of the same format regardless of which one you are talking to.
• Like with the previous bullet, even nodes that communicate among each other or with other network accessible virtual APIs, there is only one implementation in their programming logic, making the programming simpler and the resource usage on chip (of those small devices) significantly smaller.
• etc.

For several reasons including:

- Integration and fusion of data streams

- Machine learning and reasoning

- Efficient storage

- ...

Reasons:

• To make it possible to pass data from multiple different nodes through a central node without it being constantly transformed and converted (because the central node might be configured to listen for certain values via filters for special cases/events, which makes a common semantics a reasonable solution to avoid the need for complex conversions and transformations of data before being passed to filters).
• Working with a standardised communication protocol is easier than having to implement multiple libraries for multiple standards in a system that accumulates data from multiple IoT source nodes.
• Easier data querying. One engine can be modelled for a certain type of data transport format (JSON for example, which is native for most NoSQL engines).
• The possibility of making IoT nodes analogous with virtual Internet service APIs (RESTful design), removing the need to distinguish between situations where one communicates with a virtual Web service or a physical IoT node over the network. The data request data to the target is of the same format and the data received in the response is of the same format regardless of which one you are talking to.
• Like with the previous bullet, even nodes that communicate among each other or with other network accessible virtual APIs, there is only one implementation in their programming logic, making the programming simpler and the resource usage on chip (of those small devices) significantly smaller.
• etc.

Semantic interoperability allows different IoT platforms to collaborate each other, by sharing a common language. This allows to exchange data between the platforms, without needing a centralized component that translate each message. Providing semantic interoperability allows, finally, to overcome design issues in which platforms are designed as vertical solutions, and to enable horizontal approaches

From Engineering perspective, this is required to ensure the standard, the interoperability, and facilitate R&D.

There are various IoT-communication standards like OPC UA, that have a communication protocol and a standardized information model. SelfX-mechanisms, like self-optimiziation, self-configuration and plug-and-play aspects are only realizable, if we have standardised semantics in communication and information modeling. On the other side, there are communication protocols, like MQTT, that don't standardize the information modeling and have disadvantages at this point.

To ensure intelligent collaboration between connected objects in the IoT-environment- Smart home as a Digital Environment (https://www.researchgate.net/publication/275032974_Smart_Home_as_a_Digital_Environment), The end of IoT Enthusiasm or the Beginning of a new IoT Vision(https://www.researchgate.net/publication/302278861_The_end_of_IoT_Enthusiasm_or_the_Beginning_of_a_new_IoT_Vision).

Conference Paper Smart Home as a Digital Environment

Conference Paper The end of IoT Enthusiasm or the Beginning of a new IoT Vision