The last part of our event's monitoring system is to deliver the identified events to a data collector to be further analyzed. A naive implementation of such an idea would consist of having an event streamer class that interacts with a data destination, for example, Syslog:

However, this design is not very good, because we have a high-level class (EventStreamer) depending on a low-level one (Syslog is an implementation detail). If something changes in the way we want to send data to Syslog, EventStreamer will have to be modified. If we want to change the data destination for a different one or add new ones at runtime, we are also in trouble because we will find ourselves constantly modifying the stream() method to adapt it to these requirements.