SensorThings API is designed specifically for resource-constrained IoT devices and the Web developer community. It follows REST principles, the JSON encoding, and the OASIS OData protocol and URL conventions. Also, it has an MQTT extension allowing users/devices to publish and subscribe updates from devices, and can use CoAP in addition to HTTP.
The foundation of the SensorThings API is its data model that is based on the ISO 19156 (ISO/OGC Observations and Measurements), that defines a conceptual model for observations, and for features involved in sampling when making observations. In the context of the SensorThings, the features are modelled as Things, Sensors (i.e., Procedures in O&M), and Feature of Interests. As a result, the SensorThings API provides an interoperable Observation-focus view, that is particularly useful to reconcile the differences between heterogeneous sensing systems (e.g., in-situ sensors and remote sensors).
An IoT device or system is modelled as a Thing. A Thing has an arbitrary number of Locations (including 0 Locations) and an arbitrary number of Datastreams (including 0 Datastreams). Each Datastream observes one ObservedProperty with one Sensor and has many Observations collected by the Sensor. Each Observation observes one particular FeatureOfInterest. The O&M based model allows SensorThings to accommodate heterogeneous IoT devices and the data collected by the devices.
SensorThings API provides two main functionalities, each handled by a profile. The two profiles are the Sensing profile and the Tasking profile. The Sensing profile provides a standard way to manage and retrieve observations and metadata from heterogeneous IoT sensor systems, and the Sensing profile functions are similar to the OGC Sensor Observation Service. The Tasking profile provides a standard way for parameterizing - also called tasking - of task-able IoT devices, such as sensors or actuators. The Tasking profile functions are similar to the OGC Sensor Planning Service. The Sensing profile is designed based on the ISO/OGC Observations and Measurements (O&M) model, and allows IoT devices and applications to CREATE, READ, UPDATE, and DELETE (i.e., HTTP POST, GET, PATCH, and DELETE) IoT data and metadata in a SensorThings service.
SensorThings API defines the following resources. As SensorThings is a RESTful web service, each entity can be CREATE, READ, UPDATE, and DELETE with standard HTTP verbs (POST, GET, PATCH, and DELETE):[4][5]
Thing: An object of the physical world (physical things) or the information world (virtual things) that is capable of being identified and integrated into communication networks.[6]Locations: Locates the Thing or the Things it associated with.HistoricalLocations: Set provides the current (i.e., last known) and previous locations of the Thing with their time.Datastream: A collection of Observations and the Observations in a Datastream measure the same ObservedProperty and are produced by the same Sensor.ObservedProperty: Specifies the phenomenon of an Observation.Sensor: An instrument that observes a property or phenomenon with the goal of producing an estimate of the value of the property.Observation: Act of measuring or otherwise determining the value of a property.[7]FeatureOfInterest: An Observation results in a value being assigned to a phenomenon.The phenomenon is a property of a feature, the latter being the FeatureOfInterest of the Observation.
https://github.com/opengeospatial/sensorthings
https://github.com/FraunhoferIOSB/SensorThingsServer
https://github.com/nsommer/SensorThingsClient
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