Advantages of the SOA approach are

Advantages of the SOA approach are recognized in most
studies on middleware solutions for IoT. While a commonly
accepted layered architecture is missing, the proposed
solutions face essentially the same problems of
abstracting the devices functionalities and communications
capabilities, providing a common set of services and
an environment for service composition. These common
objectives lead to the definition of the middleware sketch
shown in Fig. 2. It tries to encompass all the functionalities
addressed in past works dealing with IoT middleware issues.
It is quite similar to the scheme proposed in [29],
which addresses the middleware issues with a complete
and integrated architectural approach. It relies on the
layers explained in Sections 3.2.1–3.2.5.