The searcher can choose any continuous trajectory subject to a maximal velocity constraint.
It is always assumed that neither the searcher nor the hider has any knowledge about the movement of the other player until their distance apart is less than or equal to the discovery radius and at this very moment capture occurs.
[4] A misleadingly simple example of a graph not in this family consists of two nodes connected by three arcs.
[2] In general, the reasonable framework for searching an unbounded domain, as in the case of an online algorithm, is to use a normalized cost function (called the competitive ratio in Computer Science literature).
[2][3][6] Searching a set of concurrent rays was later re-discovered in Computer Science literature as the 'cow-path problem'.