prevent title double entry

Drupal can be very efficient as a collaborative press articles archiving tool. One of the difficulties there is to prevent double entries. One way is to explain patiently to users that they HAVE to search before posting. Another way would be a simple control on the title caracter chain, hoping that a copy / past of the presse title will be recongnised by Drupal.

From there, there could be a message like "this article title is allready being used : ignore / abort".

Could this be done ?