====== Can a Context have state? ======
It can. The [[http://fulloo.info/Examples/RubyExamples/Dijkstra/|Dijkstra example]] is a good example of such a supporting data structure.
//Nodes// are one kind of object in the Dijkstra algorithm.
There are some per-node data that are germane only to the algorithm but rarely to the domains of node-ness, or of any particular kind of node, in their own right. The data is factored out into the Context.