Monitoring the UMD Shuttle service with arrival times at the bus stops,
estimation of the number of people embarking and disembarking, dynamic routing
when no passengers waiting at the stops, etc.  The requirements need to be refined.

Below is a first attempt to formulating the dynamic scheduling problem.
First, the nodes are assumed to be placed at certain fixed locations on a street network.
The weight of a node is assigned first on the appearance of a token that instantiates  
the node using by an estimate of expected arrival of the salesman. After that, the weight  
is continuously being increased by a) the time ticking and b) by the arrival of additional 
tokens at the node.
The node leaves the network (zeros its weight) when the salesman visits the node.
The non-decreasing weight is to guarantee the we will have no starvation of a node
because other nodes always enter with higher weight.