# Interoperability of the Time of Industry 4.0 and the Internet of Things
## 3 Towards Defining a Set of Key Concepts for Describing Industry 4.0 Devices
### Comparison of Different IoT Ontologies for Industry 4.0 Devices  
Table 3 below contains the most mature IoT ontologies according to LOV plus the IoT as envisioned by schema.org. For each technology, we tried to evaluate their maturity with the respect of the concepts mentioned in Section 3.1. In some cases, the implementation of the concepts is sound, while on other occasions, the concept lacks a desired level of detail; these cases are marked with an asterisk. In addition, schema.org has not yet produced a knowledge representation of the concepts, and its evaluation is based only on the preliminary discussion document. \begin{table}
\begin{tab  
The W3C Semantic Sensor Network (SSN) is one of the earliest and most reused ontologies focused exclusively on sensing and sensor data. It is meant to be supplemented with additional ontologies to fill gaps in functionality. The IoT-lite ontology was intended to be a lightweight version of the SSN ontology. The ontology was supplemented with additional functionality such as concepts for location and services. One of the premises of this ontology is to design it for optimal performance. The IoT-lite ontology is meant to be used and extended upon where needed while maintaining a lightweight set of core concepts. It proved to have increased performance over competing ontologies. The IoT-lite ontology is also submitted for standardization as a W3C standard. The Fiesta-IoT ontology composes concepts from the SSN, IoT-lite, M3 Taxonomy, Time, and DUL ontologies into the Fiesta-IoT ontology. It promises guaranteed semantic interoperability in the IoT domain. Fiesta-IoT also borrows some logic from the more complex IoT-A ontology. The M3-lite ontology is designed to facilitate the Fiesta-IoT ontology with a lightweight version of the M3 taxonomy tailored to the Fiesta-IoT project's needs. M3 taxonomy is a collection of types of sensors that are linked to the SSN sensor concept; the types of sensors range from sensors in the meteorological domain to sensors in the medical domain. Furthermore, the ontology follows best practices and uses concepts from ontologies that use best practices themselves. The ontology is used in testbeds that are part of the Fiesta-IoT project. The focus of the SSN, IoT-lite, and Fiesta-IoT ontologies is all on sensing and making sensor data semantically interoperable, with the Fiesta-IoT being the most competent in that respect. None of these ontologies goes beyond simply mentioning actuators. SEASD is a module of the larger SEAS ontology. The SEASD is a device ontology with limited concepts that allows for both sensing and actuating an object and its properties. SEASD does not reuse other existing ontologies. The IoT-O ontology is based on both the SSN and its actuating counterpart named the Semantic Actuator Network (SAN). The authors of the IoT-O ontology created the SAN themselves. The IoT-O ontology is a modularized ontology that has modules for sensing, actuating, services, lifecycle, and energy. All modules reuse existing work. Furthermore, it integrates with OneM2M standards. The IoT-O ontology was tested on a home automation use case, but offers no further details of it being currently in use in any systems. What is particularly interesting about the IoT-O ontology is the additional conception of the SAN as a basis for actuating, such as SSN for sensing, and the IoT-O's modularized design. OneM2M is not an LOV-listed ontology; however, it is supported by the OneM2M standards organization for machine-to-machine and IoT. This ontology handles actuating and device control in a more detailed manner if we compare it with SSN, which is centered on sensors. Unfortunately, the OneM2M ontology does not follow best practices and cannot be reused, since it is not freely available. Nonetheless, the logic on actuating is an important feature for Industry 4.0, and some of the concepts should serve as a base for evolving more mature ontologies in this direction.