Late on this conversation, but wanted to add to Amitoj's already good answer.

What Amitoj said is true when a notification's Send When: is Record is Inserted or Updated. But notifications behave differently when their Send When: is Event is fired and I got tripped up when I assumed it behaves the same way.

With event-triggered notifications you actually can configure an Email Notification on a parent table (e.g. Task, HR Core Case, etc.) and have it 'inherit' down to some or all of its child/extended tables.

For example, if you wanted to send an email notification any time the Short Description changes on an HR Case (the parent table), HR Payroll Case (an extended table), or HR Benefits Case (another extended table), but not the other extended tables, you could:

• Create an event (e.g. sn_hr_core.case.sd.changed)
• Create a Business Rule on the sn_hr_core_case (aka the Parent) table to fire the event whenever the short_description changes
• Configure an Email Notification, as follows:
  • Table: HR Case [sn_hr_core_case]
  • Conditions:
    • Task type [sys_class_name] is HR Case [sn_hr_core_case]
      - OR -
    • Task type [sys_class_name] is HR Payroll Case [sn_hr_core_case_payroll]
      - OR -
    • Task type [sys_class_name] is HR Benefits Case [sn_hr_core_case_benefits]

This notification configuration will result in an email being sent when the Short Description changes but only for an HR Case on one of these three tables. Alternatively, if you want the notification to send on the parent and all extended tables, you could just remove the Task type conditions.

Hope this maybe helps someone.