The discovery model is created by a business rule "Create a Software Normalization". This rule checks for the primary key data before it creates a discovery model. If the primary key of the record matched the primary key of the discovery model then it will update the matched record else it will create a new discovery model.
Business rule that creates discovery model:
The primary key field is a value that is built based on the serial number and other factors. The business rule that builds the primary key is as below.