Directed paths have been used by several authors to describe concurrent executions of a program. Spaces directed in an appropriate state space contain with all possible legal schedulings. It is interesting investigate whether one obtains different topological properties such if restricts attention schedulings "nice" properties, eg involving synchronizations. This note shows that this not the ca...

A bidirected tree is the directed graph obtained from an undirected tree by replacing each undirected edge by two directed edges with opposite directions. Given a set of directed paths in a bidirected tree, the goal of the maximum edge-disjoint paths problem is to select a maximum-cardinality subset of the paths such that the selected paths are edge-disjoint. This problem can be solved optimall...