@@ -139,20 +139,18 @@ The key words "Shall", "Shall not", "May", "Need not", "Should", "Should not" in
# 5 Introduction to OGC SensorThings API
The SensorThings API (STA) is a standard of the Open Geospatial Consortium (OGC). It provides a framework for communication and exchanging data between sensors and applications. The standard is devided in two parts. SensorThings API Part 1 is dedicated to sensing and was published in 2016 and updated in 2021<ahref="#_ref_1">[1]</a>.
The SensorThings API (STA) is a standard of the Open Geospatial Consortium (OGC). It provides a framework for communication and exchanging data between sensors and applications. The standard is devided in two parts. SensorThings API Part 1 is dedicated to sensing and was published in 2016 and updated in 2021.
A STA-based architecture works in client/server mode. A sensor device pushes data to the SensorThings Server via HTTP. A SensorThings Server may also support MQTT protocol to support publish and subscribe capabilities. An interested application can subscribe to the MQTT-Broker, in order to get notified about new sensor events.
<figcaption>Figure 5-1 STA message flow</figcaption>
</figure>

The data in the SensorThings server are organized as according to **Sensing Entities** (see Figure 5-2: Sensing Entities data model <ahref="#_ref_1">[1]</a>).
**Figure 5-1 STA message flow**
<figure>
<imgsrc="media/data_model.jpg"alt="data_model">
<figcaption>Figure 5-2 STA Sensing Entities Data Model <ahref="#_ref_1">[1]</a></figcaption>
</figure>
The data in the SensorThings server are organized as according to **Sensing Entities** (see Figure 5-2: Sensing Entities data model.

**Figure 5-2 STA Sensing Entities Data Model**
In the Sensing Entities Data Model events or sensor data are called "observations". Before a sensor is able to push an observation to the server it needs at least a 'Thing' and a 'Datastream' entity. This has to be created beforehand. One 'Thing' might have different 'Sensors', one 'Location' or many 'HistoricalLocations'.
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@@ -171,10 +169,9 @@ Figure 6.0-1 shows an architecture approach for an Interworking Proxy Entity (IP
The basic interworking enables applications that are connected to an oneM2M-based system to get data from sensors that are connected to an OGC/STA server. Furthermore, an application that is connected to an OGC/STA server will be able to get data from sensors that are connected to an oneM2M-based system.
@@ -184,11 +181,9 @@ According to oneM2M TS-0033 <a href="#_ref_2">[2]</a> a representation of a non-
The IPE shall map the 'result' attribute of an OGC/STA 'Observation' to the 'content' attribute of a oneM2M <contentInstance>, and vice versa as shown in Figure 6.1-1.