Backpaths

Backpaths is a term used in several technical fields to describe paths that are considered in reverse relative to a forward path, or routes used to backtrack from a destination to a source during analysis. It is not a formal term with a universal definition; its precise meaning is domain-specific.

In graph theory and algorithms, a common use is during path reconstruction: after a search such as Dijkstra's or A*, the actual route is recovered by following predecessor pointers from the target back to the source; this reverse sequence is often described as a backpath. In bidirectional search, backpaths can refer to the portions of the path traced backward from each search front.

In networking and routing, backpaths refer to reverse or return routes used for control messages, acknowledgments, or path verification; some protocols treat the backward route as a complement to the forward path, aiding in loop avoidance and fault recovery.

In algorithm design, backpaths appear in backtracking methods: the current partial solution defines a backpath, and when a dead end is reached, the algorithm traverses the backpath to undo decisions and explore alternatives.

Due to its variable usage, the term should be defined by the author when employed, and it is often used interchangeably with related concepts such as reverse path, backtrace, or predecessor path.