Hypermedia

An extension of hypertext that incorporates multimedia content — audio, video, images, and animation — alongside text, all linked in a non-linear structure. What distinguishes hypermedia from hypertext is the implied sequencing required for time-based media: a video contains image sequences, audio tracks, and potentially closed captions that must be synchronised. This synchronisation has direct accessibility implications, as captions must be timed to speech, audio descriptions must fit between dialogue, and alternative content must be coordinated across modalities. The Amsterdam Model of Hypermedia formalised these timing relationships by extending the Dexter Model with synchronisation arcs and channels.