On middle vs passive in Polish and Russian (and, if possible, Ukrainian)

[Loren A. Billings]

Can anyone enlighten me on the crucial distinctions between passives and
middles in Pol and Rus (and Ukr).  As I understand the situation (based
primarily on Babby's framework) for Russian, the passive is expressed in
Rus using eith an imperfective verb with -sja or a perfective verb in its
past-passive participial form.  Imperfective verbs in past-prt form are
all but ungrammatical in CSR.  Perfective verb stems with -sja can only be
middles (testable because an INST-case 'by' phrase is bad with these).
The middle is expressed with either a perfective or and imperfective verb
stem with -sja (with no middles can there be an INST 'by' phrase).  Middles,
of course, often have adverbials:  _Dver' legko otkryvaetsja/otkryvalas'._
Is all this also the case with Pol and Ukr?  It would appear to be the
case with Ukr, but seems to be quite the opposite in Pol (as one comment
leads me to believe).  Again, I'd appreciate your comments by midday or so
on Monday, if possible.  Best,  --Loren Billings (billings at princeton.edu)