Hi,
I am having trouble working out how to model this situation correctly in UML.

Thread 1 and 2 are running concurrently

.... |-->thread1
-->|
.... |-->thread 2

Thread 1 is running, but when an event occurs, thread 1 creates a new thread, thread 3... however thread 1 continues running.

All of the examples I have seen show a split followed by a join - is it ok to show thread 1 splitting to create thread 3 and going back to itself? As this means there is no need for a join?

So basically I need to show that after creating a new thread the existing thread continues running.

....|------\
...\/............|__|
thread 1 -->|--->thread 3

Sorry not a very good diagram, but thanks If you can understand this!

To try and make this clearer... thread 1 is listening for incoming message
thread 3 is processing message.

So when a message arrives, a new thread is created to process it, however the existing thread continues listening.

Thanks for any help!