In case you missed it last week on Sticky Bits:

Software Duct Tape -- Binding the C++  Universe Together

by Glennan Carnie

From the article:

One of the cornerstones of object-oriented design is the concept of objects interacting by sending messages to form mechanisms – units of higher-order (or ‘emergent’) behaviour.

In order to send a message (in this case, invoke a member function) an object must have a ‘link’ to the target object. That link is formed by building in an association between the two classes as part of the type’s definition.

In this article we look at building associations between classes and forming run-time links so objects can communicate...