how to recognize a file as IDEA meta-file

hello,
is there a way to recognize a file as IDEA meta-file (.ipr, .iws, .iml, xml placed under .idea content root for directory-based projects) ?
Or do I have to do it manually (check file extension / check whether it is a child of .idea meta-directory - for directory-based projects) ?
thanks in advance for any assistance,
regards
Simon