Is it possible to return string from Task?

Absolutely!
You can return any type that RSG supports - string, [ ], { }... any JSON sausage you can think of, plus a few more.

Thank you for your reply.

Can you just give an example how you will get the string value from Task component to Scene component.

I accept we can set the value for interface, but how will you return string from a function in Task Component.

For example:

m.taskContent = createObject("roSGNode","contentReader")
m.taskContent.FunctionName="getProcessType"
m.taskContent.Control="RUN"

processType =""
processType = m.taskContent.ProcessType

is it possible like this? or in any other way?

Use this code in your Scene component:

m.taskContent.ObserveField("ProcessType", "onProcessType")

sub onProcessType()
    print "ProcessType: "; m.taskContent.ProcessType
end sub

Yea i am doing like this only, it is working fine mate.
Thanks for your reply