A Visual Paradigm for IoT Solutions Development - Interoperability and Open-Source Solutions for the Internet of Things - page 41

Fig. 10. Widgets of the Request Presentation

it has shown that developers can use the presented tools for creating a baseline service,
which they can further enhance through additional coding/development outside of the
scope of the visual tools.

5 Conclusions

Despite the emergence and proliferation of middleware frameworks for developing and
deploying IoT applications, nowadays there are still only a limited number of envi-
ronments and tools for the visual development of IoT applications. These environments
are typically focused on certain low-level aspects of IoT applications such as nodes
connectivity in WSN and the management of RFID devices. Hence, they are not
suitable for supporting the development and deployment of integrated IoT applications,
which leverage data from the wide range of physical and virtual sensor sources that
comprise the IoT paradigm. In this paper we have introduced a visual environment,
which facilitates the development of IoT applications with minimal (almost zero)
programming effort. The visual environment operates over the OpenIoT architecture,
which uses the W3C SSN ontology as its main semantic model for describing sensors
and related IoT context. Modeling IoT services using the presented tool is based on
the speci cation of a graph, which corresponds to an IoT application. The nodes of the

graph correspond to (sensor) data sources, processing components, as well as pre-
sentation components. Every graph can be validated through the tool and accordingly