Hi
1.I have a doubt in Start Event usage.
If my Process is starts with Signal Start Event, then it is required to have source trigger from Signal throw event alone? or any Task , SubProcess, Intermediate events of any type ?
Note: Same doubt is for Message,Timer and Conditional Start events
2.Similary intermediate events like message, timer, Conditional ,signal need to get trigger source from throw events of its own pattern or any other task , sub process ?
Some events like signal and messages can be triggered by a corresponding send event. They can also be triggered programmatically via the Java or Rest API.
Other events like timers and conditional events are not triggered by other events. As their name suggests they are triggered by elapsing time and conditional changes.
Which means , Any Task and Sub Process resulst could be a source trigger rite ?
It depends on the event - for messages and signals they can be triggered from anywhere even external sources.
So, Not Necessarily Signal Start Event should get trigger only from Signal Throw event.
Also from any other Task or SubProcess (Programmatically) am i right?
Yes.
You might find this documentation useful - it explains how to use signal events in more detail:
https://docs.camunda.org/manual/7.9/reference/bpmn20/events/signal-events/