Internet of Things – Architecture © - 56 -
and Human User in the case of ―Ted‖. What these entity categories mean and
how they relate to each other is discussed in detail in the next sections.
In addition to the coloured boxes, the diagram also shows arrows with verbs
that connect the boxes. If we look very closely to the arrows, we see that they
have different terminators such as diamond shapes or traditional arrow shapes.
These shapes illustrate different kinds of relationships between the objects that
are connected by them. In a similar way as the category names and the colour
coding of the objects are related to each other, the verbs indicate information
about the relationships shown with the arrows. These are all concepts of the
UML notation that will be discussed in the next section.
Even without understanding all of the concepts in detail, we can already
understand that the IoT Domain Model helps us structuring an application
scenario. We can use a concise graphical representation to show that for
instance ―Ted‖, our truck driver, is a Human User that uses an Android
application in order to subscribe to an Alarm service. This Android Application is
an Active Digital Artefact (ADA). We do not yet know what this exactly means,
but as the reader will progresses through this document and possibly other
documents that make use of the IoT Domain Model, Active Digital Artefacts will
come up again and again. By providing a standardised vocabulary for naming
things that relate to the same abstract concepts, we facilitate and streamline
communication of the IoT ARM users.
While several other parts of the IoT Reference Model, for instance the IoT
Information Model, directly depend on the IoT Domain Model, and also several
views (as we will see in the next chapter), it should already be noted that the
IoT Domain Model also takes a central role in the process of generating
concrete architectures beyond merely providing a common language. As
discussed in Section 5.2.4, there is a special view called IoT Context View that
is central in the process of generating concrete architectures. This view is an
amalgam of the IoT Domain Model ‖traditional‖ context view. The latter is an
architecture view that is usually generated at the very beginning of the
architecture process. It describes ―the relationships, dependencies, and
interactions between the system and its environment (the people, systems, and
external entities with which it interacts).‖ [Rozanski 2012]
3.3.2 Main abstractions and relationships
3.3.2.1 Interpreting the model diagram
This section describes the IoT Domain Model used in the IoT-A project. It was
mainly developed by refining and extending two models found in the literature
[Haller 2010] and [Serbanati 2011]. The goal behind the IoT Domain
Model is to capture the main concepts and the relationships that are relevant for
IoT stakeholders. After a short introduction to the pertinent UML language (next