The four components of the production line are: a storage rack, a filling machine, a robotic arm and a packaging machine. If there exist multiple machines of the same type in the factory, we need to know which one is connected to what. The pattern for describing connections follows the SAREF for System ontology ([SAREF4SYST](https://saref.etsi.org/saref4syst/)). Each machine is a `s4syst:System` that has `s4syst:ConnectionPoint`s. A connection point is attached to a `s4syst:Connection`, which is a physical or virtual entity that represents the connection between 2 systems.
We simplify the situation a little by assuming that the area of the output product and the area of input material are the same as the points of connection, and we will consider that the connection is a single point. So, for the sake of this summer school, we assume that the absolute coordinates of the output location of the storage rack is exactly the same as the input location of the filling machine. Note that the blue dashed lines in the diagram are relations that one can infer from the ontologies; they are not necessarily present in the knowledge graph.
In the case of the robotic arm, there is no connection, because it can move freely. The robotic arm must be able to position its arm at the output location of the filling machine, and move the pots to the input location of the packaging machine.
## Coordinate systems in more detail
The coordinates are given in a cartesian reference frame that is relative to a larger cartesian frame. For instance, each machine is located at coordinates defined with respect to the IT'm factory, while components of a machine are located at coordinates relative to the machine itself. This way, the components of a rigid machine are located once and for all, even if the machine moves. The precise description of the coordinates is given by the following diagram (**TO BE COMPLETED**).
## Relations between sensing/actuating devices, observable/actuatable properties, and property/action affordances
We can relate properties of the real world, devices that sense or act upon those properties, and the thing APIs that can get access to the observations or actions of/on these physical properties. (TO BE COMPLETED)
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We can relate properties of the real world, devices that sense or act upon those properties, and the thing APIs that can get access to the observations or actions of/on these physical properties. For this, we are using the [SOSA/SSN ontology](https://www.w3.org/TR/vocab-ssn/).
