Distinguishing between what someone else does prior to filing versus what inventor does.
a.    Ex. Japan allows you 6 months to file from your own disclosure but you are barred once someone else discloses.
b.    Who would take advantage of grace period if you knew somebody else disclosing would destroy your patent right? Need to protect first.
c.    Evidentiary problem: If I make invention public, need to make sure someone else doesn’t “make it public” to create a bar to my patenting. Perhaps prove path of derivation showing that they didn’t disclose merely because you did.