So if I'm understanding this correctly, the SC could be defined as something like "a list of link/node pairs". Then the master template that is displaying the list would always know what data structure it is going to get when it makes the SC call.
How you generate the data depends on your choice of implementation of the SC. So one implementation could behave the same as the current ad_context_bar (although "a supplemented list of link/node pairs" might be a better description of the SC in this case; ie. you allow the SC call to specify additional link/node pairs). Whereas another implementation generates pairs based on the actual route taken by the user.
In which case we would also want other kinds of SC for other kinds of data structure that hold navigation elements; eg. "a tree of link/node pairs". Or am I missing the point? :)
