This is basically a metric with tags. Only difference is that a metric has a main unit it measures. In the end anything can be represented as a structured log.

This is basically a metric with tags. Only difference is that a metric has a main unit it measures. In the end anything can be represented as a structured log. A span is NOT what the OP calls a “system wide event”. A span has a begin and end time. What he/she describes doesn’t have that. In the end giving different kind of instrumentation instruments a name makes sense, mainly for processing them / rendering them / altering on them.