HyTime
Hypermedia/Time-based Structuring Language: an emerging ANSI/ISO Standard from the SGML Users' Group's Special Interest Group on Hypertext and Multimedia (SIGhyper). A hypermedia extension of SGML.
["The HyTime Hypermedia/Time-based Document Structuring Language", S. Newcomb et al, CACM 34(11):67-83 (Nov 1991)].