The MainJob and Replicator classes could turned to Abstract or I could introduce new base classes. I had previously deleted the Job class but this needs reinstating with MainJob extending Job. Then there could also be a replication base class that then extends the Job class functionality and introduces the functionality associated with spawning a Job. The base class in this instance could be referred to as SpawnableJob. I have chosen to introduce base classes mainly because I prefer the names of the base classes.
In future Job Classes could have further functionality added e.g a job with attached documents.
This would require minimum amendments to the JobDatabase class.
The class diagram now looks like this:
