cnn's barbara starr is live at the pentagon with the details this. good morning, barbara. >> good morning, john. we've talked so much abo ts notion of a bomb signature. what is it a why is it impoant? you know, bombmakers tend to put their bombsoghehe same way each andve time and when they train others to put a bombether that is the bomarssignature. what experts are doing is atatia was used?orensics. how was it put together? what kind of detonator? what kind of fuse? w was the bomb placed, if you will? signature.se things make uhe andhes aas body of in afghanistan, through iraq, terrorist attacks overseas, liryas put together e hundreds, if not thousands, of