Directed graph

A mathematical structure consisting of nodes connected by edges that have a defined direction — the connection from A to B is distinct from the connection from B to A. Web navigation is modelled as a directed graph: a hyperlink from page A to page B does not imply a link back from B to A. This one-directional nature of HTML links is a constraint inherited from the Dexter Model and has direct accessibility implications. Screen reader users navigating by links can follow a path forward but must rely on browser history to return, and there is no structural guarantee that the return path is meaningful. Bidirectional linking, supported by the Dexter Model but not implemented in HTML, would allow assistive technology to understand and present both directions of a relationship between content.