There are good specs documents about it around the net. they can specify a lot of scene settings in what's related to materials: specularity, etc, etc.basic use is it will point to a texture for the model.
http://www.wotsit.org/list.asp?fc=2
and obj specs, just in case:
http://netghost.narod.ru/gff/vendspec/w ... j_spec.txt
arent the best links, just the ones I triggered in a 6 seconds google ping
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