  We propose a new method for computing the language intersection of two Time
Petri nets (TPN); that is the sequence of labels in timed traces common to the
execution of two TPN. Our approach is based on a new product construction
between nets and relies on the State Class construction, a widely used method
for checking the behaviour of TPN. We prove that this new construct does not
add additional expressive power, and yet that it can leads to very concise
representation of the result. We have implemented our approach in a new tool,
called Twina. We report on some experimental results obtained with this tool
and show how to apply our approach on two interesting problems: rst, to dene an
equivalent of the twin-plant diagnosability methods for TPN; then as a way to
check timed properties without interfering with a system.
