Clever way to check overlapping time intervals ?

Hi,
is there a clever way to check overlapping time intervals ?
An option named n should be taken from date y to y.
The same name is ok for another interval.

e.g. table :  mytab ( d1 date, d2 date, n text, v text )

There should be a constraint to provide no row can have a d1 or d2 
within the interval of another row in case they have the same n.

And no row can have an interval that encloses an existing interval.