Internet of Things Architecture

Internet of Things – Architecture © - 59 -

two key entities of the IoT. The User is a human person or some kind of a
Digital Artefact (e.g., a Service, an application, or a software agent) that needs
to interact with a Physical Entity.

In the physical environment, interactions can happen directly (e.g., by moving a
pallet from location X to Y manually). In the IoT though, we want to be able to
interact indirectly or mediated, i.e., by calling a Service that will either provide
information about the Physical Entity or act on it. When a Human User is
accessing a service, he does so through a service client, i.e., software with an
accessible user interface. For the sake of clarity, the service client is not shown
in Figure 10. For the scope of the IoT Domain Model, the interaction is usually
characterised by a goal that the User pursues. The Physical Entity is an
identifiable part of the physical environment that is of interest to the User for the
completion of her goal. Physical Entities can be almost any object or
environment; from humans or animals to cars; from store or logistics chain
items to computers; from electronic appliances to jewellery or clothes.

User Physical Entity

0..*

interacts

with

0..*

Figure 9 : Basic abstraction of an IoT interaction.

Physical Entities are represented in the digital world by a Virtual Entity. This
term is also referred to as ―virtual counterpart― in the literature [Römer 2002],
but using the same root term ―entity― in both concepts clearer shows the
relationship of these concepts. There are many kinds of digital representations
of Physical Entities: 3D models, avatars, database entries, objects (or instances
of a class in an object-oriented programming language), and even a social-
network account could be viewed as such a representation, because it digitally
represents certain aspects of its human owner, such as a photograph or a list of
his hobbies. However, in the IoT context, Virtual Entities have two fundamental
properties:

 They are Digital Artefacts. Virtual Entities are associated to a single

Physical Entity and the Virtual Entity represents this very Physical Entity.

While there is generally only one Physical Entity for each Virtual Entity, it

is possible that the same Physical Entity can be associated to several

Virtual Entities, e.g., a different representation per application domain.

Each Virtual Entity must have one and only one ID that identifies it

univocally. Virtual Entities are Digital Artefacts that can be classified as

either active or passive. Active Digital Artefacts (ADA) are running