Operators used In locks:
& - means AND, @lock gate = key & passport means BOTH are necessary.
| - means OR, @lock gate = Key | Passport means one of them is enough.
! - means NOT, @lock gate = !gun means that you can't pass with a gun.

()- declare precedence, @lock Gate=(key|passport)&!gun
  means a key, or a passport (or both) as long as there's no gun.

: - means MEMBER_OF,  @lock gate = passport:+stamped_by_immigration
 means that passport has to be a member of group +stamped_by_immigration.

See also: @lock, lock, locks, @effect, logic