Uv's Re-Uv

Uving a mesh requires you to make seams to make Blender understand how to unwrap it , but sometimes i find myself having exported models in obj and reimporting them back , and losing the seams , insthead of doing seams from scratch it would be very great to have Blender DEDUCE the seams based on the UV edges , so then you can RE-UV and have blender recalculate the uv's