Internet of Things – Architecture © - 64 -
The instance diagrams such as Figure 5 are concrete instantiations of the IoT
Domain Model, i.e. concrete architectures modelled with the concepts of the IoT
Domain Model.^
3.3.3 Detailed explanations and related concepts
The IoT Domain Model as explained in the previous section is focusing on the
main concepts at a high level of abstraction, capturing the essence of the IoT
domain. However, for easier understanding we provide here more detailed
explanations.
3.3.3.1 Devices and device capabilities
From an IoT Domain Model point of view, Devices are only technical artefacts
meant to provide an interface between the digital and the physical worlds, i.e. a
link between the Virtual Entities and the Physical Entities. For this reason,
Devices must be able to operate both in the physical and digital world and the
IoT Domain Model only focuses on their capability to provide observation and
modification of the physical environment from the digital environment. If other
properties of Devices were relevant, the Device would be modelled as an entity
itself.
The hardware underlying the Devices is very important though and must have
at least some degree of communication, computation and storage capabilities
for the purposes of the IoT. Moreover, power resources are also very important,
as they can provide operational autonomy to the Devices. Many technologies
and products are available and their capabilities vary noticeably. While these
capabilities might not impact directly the IoT Domain Model, they are very
important during the application-design phase, c.f. the Deployment and
Operation View in Section 4.2.4.
Communication capabilities depend on the type of data exchanged with the
Device (identifier, identifier + data, sensor data, or commands) and the
communication topology (network, reader-tag, peer-to-peer, etc.). These
aspects are very important in the IoT context and have a large impact on energy
consumption, data-collection frequency, and the amount of data transmitted.
Communication capabilities indirectly impact the location of Resources (on-
device or on the network). Please refer to the IoT Communication Model
(Section 3.6) for a detailed discussion of this topic. Security features also impact
communication capabilities, since they usually introduce a relevant
communication overhead (c.f. Section 3.7).
Computation capabilities on the other hand have a huge impact on the chosen
architecture, the implementable security features, and power resources of the
Devices. They are also relevant for what concerns the availability of On-Device
Resources and their complexity, as constrained Devices might not have
sufficient computational resources.