2 Markers and a run-in

I'm wondering for a couple of days how the following example would be
rendered using CSS2.
(I need to know it for implementing css2)

[*] = not part of the document-tree
:before and :after are acting like a sibling

* Part of example document-tree
 [*] R:before (marker)
  *  R (run-in)
 [*] P:before (marker)
  *  P (block-box ; non-floating ; not absolutely positioned)

Would it result in a block-box 'P' containing R as an inlinebox and having
R:before and P:before as a marker?

greetings,

Mark