In order to find the desired sensor, there needs to be a way to specify what kind of sensor the application is looking for. In this API there are two qualifiers for this purpose: the quantity and the context type. They form the basis of the sensor ontology of this API. The application can use either one independently or specify both. When used together, the both must match.

Context types categorize sensors into four groups:

By using context types, it is possible to find, for example, user-related sensors for fitness, or ambient sensors for smart home controlling. Although the granularity of this level does not qualify the sensors very precisely, still in some cases it provides the way to make the distinction, for example, cf. air thermometer (ambient) / clinical thermometer (user).

The quantity provides a more precise qualifier. The unit and the quantity has a close relation. Some quantities are listed in tables of Unit class. When the quantity and context type is known, it is often easy to guess the full purpose of the sensor. Some examples are given here:

    Quantity: electric_current + context type: ambient = 
    sensor measuring electric current, amperemeter

    Quantity: catalytic_activity + contex type: ambient =
    sensor measuring catalytic activity
    

Sensor examples

To help the user to find the sensor, some ready made combinations and the sensor following from the definition, are presented here.

Table A.1.  Examples of defining sensors with quantity and context type