First of all, we need to understand Correlation w.r.t. TrueSight Event Management. In simple words, if you know the Cause and Effect of any Event Reported, you can correlate the scenarios in TrueSight via Event Mgmt Policies or MRLs.
Secondly, around Business Service Impact Models, there are 3 ways you can achieve it -
1) BMC Discovery (SAM Models) ---> CMDB (Service Models) --->TrueSight (Service Impact Models Models)
2) Atrium CMDB (Impact Model Designer - Service Models) -->Publish in TrueSight
3) TrueSight (SIM Models).
When a Service Model is prepared you can actually define weightage around the components and maintain 2 Status for each of the services -
1) Service Degraded.
2) Service Down.
Now the question comes "HOW TO REDUCE COUNT OF INCIDENTS IN INFRA via MONITORING SOLUTION?". BMC Service Resolution can give you multiple ways to raise incident from TrueSight into Remedy Incident Management. This can trigger One Incidents reported via Multiple Events as per Service Model configured.