Question on presenting in conferences

[Sonit Sisolekar]

I have heard that it is unethical to publish the same paper in a conference and in a journal at the same time.

But is it ethical to present the same abstract in multiple conferences? Suppose we present an abstract at a conference, but afterwards had to revise it or add something to it. So, is this revised abstract accepted to present in some other conference? Is it ethical?

Yours Gratefully

Sonit Sisolekar