334
R. Gonzalez-Usach et al.
layers: Device-to-Device (D2D), Networking-to-Networking (N2N), Middlewareto-Middleware (MW2MW), Application and Services-to-Application and Services
(AS2AS), Data and Semantics-to-Data and Semantics (DS2DS) [15].
3.4.1 Semantic Interoperability Layer
ACTIVAGE makes use of the following layers of INTER-IoT to achieve semantic
interoperability among different IoT platforms:
• Middleware-to-middleware layer (MW2MW) [36, 37]: the interoperability
solution for the middleware level is based on the use of an abstraction layer that
connects to all the IoT platforms and provides access to all their data and resources
through a common API. The core of the MW2MW layer is a broker, which handles
the different communication flows in real-time. The MW2MW connects to the
platforms using bridges that act as syntactic translators between the data formats
of the platforms and the common Inter-IoT data format (JSON-LD) in addition to
performing some communication functions. This layer also maintains a registry
of all the connected platforms and devices and provides a common representation
of these resources. The MW2MW solution, also known as Inter-MW, is responsible for providing syntactic interoperability and for enabling and managing the
communication between platforms.
• Semantics and Data layer (DS2DS) [6]: the interoperability solution for the
DS2DS layer provides semantic interoperability based on semantic translation
between the different platforms’ ontologies and a central modular ontology [18,
38]. This way, a common meaning of the data and information is achieved, thus
enabling semantic interoperability among different platforms. The Inter Platform Semantic Mediator (IPSM) [6] is the component that performs the semantic
translation of the data using ontology alignments.
The combination of both aforementioned solutions is called the Semantic Interoperability Layer (SIL) and is the key component that makes it possible for the
ACTIVAGE deployment to enable and ensure semantic interoperability in DSs.
Inter-MW (MW2MW Layer) provides a common API to access all the data and
resources of the connected platforms and performs the syntactic translations between
the common ACTIVAGE JSON-LD format and the platforms’ formats. The data in
JSON-LD (an RDF serialization) is sent to the IPSM (Inter-IoT DS2DS Layer) to
perform the necessary semantic translations to/from a common central ontology to
platform-specific semantics. This translation process is explained in more detail in
the following section.
Since the SIL provides a common syntax and semantic representation of the data,
the services and applications built on top of the SIL will be able to use the information
coming from any of the connected platforms. Also, by using the SIL, the information
can be shared among different platforms and its meaning can be understood by any
of them. Once the data have been translated by the IPSM into the target platform
R. Gonzalez-Usach et al.
layers: Device-to-Device (D2D), Networking-to-Networking (N2N), Middlewareto-Middleware (MW2MW), Application and Services-to-Application and Services
(AS2AS), Data and Semantics-to-Data and Semantics (DS2DS) [15].
3.4.1 Semantic Interoperability Layer
ACTIVAGE makes use of the following layers of INTER-IoT to achieve semantic
interoperability among different IoT platforms:
• Middleware-to-middleware layer (MW2MW) [36, 37]: the interoperability
solution for the middleware level is based on the use of an abstraction layer that
connects to all the IoT platforms and provides access to all their data and resources
through a common API. The core of the MW2MW layer is a broker, which handles
the different communication flows in real-time. The MW2MW connects to the
platforms using bridges that act as syntactic translators between the data formats
of the platforms and the common Inter-IoT data format (JSON-LD) in addition to
performing some communication functions. This layer also maintains a registry
of all the connected platforms and devices and provides a common representation
of these resources. The MW2MW solution, also known as Inter-MW, is responsible for providing syntactic interoperability and for enabling and managing the
communication between platforms.
• Semantics and Data layer (DS2DS) [6]: the interoperability solution for the
DS2DS layer provides semantic interoperability based on semantic translation
between the different platforms’ ontologies and a central modular ontology [18,
38]. This way, a common meaning of the data and information is achieved, thus
enabling semantic interoperability among different platforms. The Inter Platform Semantic Mediator (IPSM) [6] is the component that performs the semantic
translation of the data using ontology alignments.
The combination of both aforementioned solutions is called the Semantic Interoperability Layer (SIL) and is the key component that makes it possible for the
ACTIVAGE deployment to enable and ensure semantic interoperability in DSs.
Inter-MW (MW2MW Layer) provides a common API to access all the data and
resources of the connected platforms and performs the syntactic translations between
the common ACTIVAGE JSON-LD format and the platforms’ formats. The data in
JSON-LD (an RDF serialization) is sent to the IPSM (Inter-IoT DS2DS Layer) to
perform the necessary semantic translations to/from a common central ontology to
platform-specific semantics. This translation process is explained in more detail in
the following section.
Since the SIL provides a common syntax and semantic representation of the data,
the services and applications built on top of the SIL will be able to use the information
coming from any of the connected platforms. Also, by using the SIL, the information
can be shared among different platforms and its meaning can be understood by any
of them. Once the data have been translated by the IPSM into the target platform