This link has the break down
http://clang.llvm.org/docs/AutomaticReferenceCounting.html#ownership.spelling.property
assign implies __unsafe_unretained ownership.
copy implies __strong ownership, as well as the usual behavior of copy semantics on the setter.
retain implies __strong ownership.
strong implies __strong ownership.
unsafe_unretained implies __unsafe_unretained ownership.
weak implies __weak ownership.