A rich hypertext facility used in SGML (StandardGeneralizedMarkupLanguage) documents. XLink is to HyTime as XML is to SGML.
From http://www.oasis-open.org/cover/hytimeKimber9701.html :
"HyTime is an application of SGML: to oversimplify, HyTime defines a set of element types that you can use with your existing SGML document types to provide hyperlinking and other facilities in a standardized way.
In other words, HyTime effectively extends SGML by defining a standard set of facilities for doing hypertext and multimedia presentations.
HyTime does not compete with or change SGML in any way--it simply builds on the basic facilities SGML provides. In particular, HyTime provides the following hypertext-related facilities:
See also: http://www.oasis-open.org/cover/hytime.html