CxObjects are the basic building blocks used to construct a
commodity. A commodity uses CxObjects to take care of all
manipulations of CxMessages. When a CxMessage "arrives" at a
CxObject, that CxObject carries out its primitive action and then, if
it has not deleted the CxMessage, it passes the CxMessage on to the
next CxObject.  A commodity links together CxObjects into a tree,
organizing these simple action objects to perform some higher
function.

A CxObject is in one of two states, active or inactive.  An active
CxObject performs its primitive action every time it receives a
CxMessage.  If a CxObject is inactive, CxMessages bypass it,
continuing to the CxObject that follows the inactive one.  By d
efault, all CxObjects except the type called brokers are created in
the active state.

   Figure 1: The Commodities Network