  Good frames were suggested in [Sh:h] as the (bare-bones) parallel, in the
context of AECs, to superstable (among elementary classes). Here we consider
$(\mu,\lambda,\kappa)$-frames as candidates for being (in the context of AECs)
the correct parallel to the class of $|T|^+$-saturated models of a strictly
stable theory (among elementary classes). One thing we lose compared to the
superstable case is that going up by induction on cardinals is problematic (for
stages of small cofinality). But this arises only when we try to lift such
classes to higher cardinals. Also, we may use, as a replacement, the existence
of prime models over unions of increasing chains. For this context we
investigate the dimension.
