Let's say a morphism $f:X\to Y$ is **compactifiable** if it admits a factorization $f = pj$ with $j:X\to P$ an open immersion and $p:P\to Y$ proper. 


In SGA 4 Exp. XVII, Deligne says that Nagata proved that any morphism of separated integral northerian schemes is compactifiable but that he didn't understand the proof.


My questions: 


* Where can I find a proof of Nagata's theorem?
* What about the complex analytic setting?



Compactifiable morphisms
Brian Conrad has written up a proof of Nagata's theorem, starting from notes of Deligne: <http://math.stanford.edu/~conrad/papers/nagatafinal.pdf>. About the analytic case, I have no idea.


