Here is the current model of the crx scene

SCENE      ZONE---VIEW
            |      |
           ZONE   VIEW

ZONE       DCS---LMODEL

DCS     crx_node--MATRIX--DCS--DCS--DCS

LMODEL     LIGHT
             |
           LIGHT

Thats pretty much all of interest - the crx_node in the DCS
tree is either an INSTANCE of a LIGHT. Lights no longer contain
directional information, they are embedded in a DCS node from which
they inherit a matrix. Thus both INSTANCEs and LIGHTs have a DCS pointer
embedded, which simply points back to the DCS node which contains them,
allowing the user to get a hook back into the tree.