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Semantic Technologies for IoT
The ontology excludes a hierarchy of sensor types; these definitions are left for domain
experts to decide, based on the workings of the sensors.
SSN defines high-level concepts for representing sensors, their observation, and the
surrounding environment. However, according to the W3C SSN ontology final report,
SSN has several limitations:
• Common terms to represent subclasses of ssn:Sensor type, measurement type,
unit type, or domain type (ssn:FeatureOfInterest) are not made available in the
ontology. This limitation hinders machine automation.
• Domain concepts like time and locations are not included in SSN. But via OWL
imports, these concepts can be included from other ontologies. This may result in
interoperability issues between domain ontologies, since domain ontologies that
are related to IoT are not standardized.
Observation
Sensing
device
At
Measures
Using
Location
Measurement
property
Unit
Made by
FIGURE 13.5
Sensor activity illustration.
Deployment
System
O peratingRestriction
PlatformSite
Device
Data
Skeleton
MeasuringCapability
C onstraintBlock
Process
FIGURE 13.6
Overview of the semantic sensor network ontology modules.