TalkChess.com

[Pawel Koziol]

The term "outpost" is confusing, because it is close, but not identical, to a piece in the hole of enemy pawn structure. Nimzowitsch in "Mein System" required a defending pawn and a half-open file, showing explicit examples like white pawns on c2 and e4, black pawns on c7, d6 and e5, white knight on d5. Black might play c7-c6, but then he is saddled with an undefended pawn on d6.

Having said that, I was always better off evaluating "holes" rather than "outposts" (but adding additional bonus for a defending pawn). Furthermore, I know of no program making use of a "half open file" requirement.
_________________
Pawel Koziol
http://www.pkoziol.cal24.pl/rodent/rodent.htm