I have some questions regarding keyed data, publishers and subscribers. I have seen keyed data examples where a data writer must register as a provider of a specific flavor of keyed data; for instance, sensor data with a sensor id as the key. The DDS interface supports the notion of a publisher registered as a provider of a specific flavor (instance) of sensor data. I have seen examples where subscribers register for *all* instances of sensor data, i.e. TOPIC only, however, I have yet to find an example where a subscriber can register as a consumer of a specific instance of sensor data.
My questions are:
1. Does the DDS specification support the notion of a subscriber’s ‘registration’ as a consumer of a specific instance of keyed data. 2. If so, how is this implemented? Specifically, if there exists a publisher of sensor data with key = sensor_id = 5 , and a subscriber of sensor data with sensor_id = 7, will there be data transfer between these two entities that is somehow filtered at the subscriber end? Or, is connectivity not ever established between these entities? 3. What does this look like in code?