9D

Directory Definition File Name carries the AID of a directory file used during application selection - a structural, navigational tag rather than an application-identifying one: where the AID in 4F (covered earlier) names an actual payment application a terminal can select and transact with, 9D names a directory a terminal has to look inside first, one level up from any actual application. It's related to 4F, since both carry AID-shaped values, and to the Application Template (61, covered earlier), the same constructed record structure that can hold either kind of entry depending on whether it's describing a real application or a further directory to descend into. A terminal's directory-traversal logic needs to distinguish the two cases correctly - treating a 9D entry as if it were a directly selectable application, or vice versa, produces a SELECT command aimed at the wrong kind of target, which fails in a way that looks like a card compatibility problem rather than the terminal-side directory-navigation bug it actually is. See EMV 4.4 Book 3.