what's the use of correlation, is there an example explain it?

[elim19]

In spec, it says define event correlation rules. how could I use it in actual cases?
In examples, I do see cases using correlation, but not get what it tries to do, for example, in https://github.com/serverlessworkflow/specification/tree/main/examples#monitor-patient-vital-signs-example, what is the point defining "contextAttributeName": "patientId" in events?
Is it to pass to argument or used in DataFilter?

[tsurdilo]

hi, duplicate of #748 right?