[Orgmode] how to establish relation relation between (states of) different projects?

[Peter Tury]

Hi

is this possible in a simple way? I mean the following. Many times
some (otherwise "idependent") projects relate to each other somehow.
E.g. I have proj-x and proj-y on the same level: they are not under
each other, so neither of them is a "subproject" of the other. Let's
say proj-x must reach state A (e.g. a specific TODO must be DONE under
proj-x) before proj-y can go forward. Can I somehow code this into my
.org file? E.g. I would like to SCHEDULE one of proj-y's TASK to the
next day when a given TASK of proj-x's is DONE. How to do this easily?

Thanks,
P