This document specifies the second version of the Synchronized Multimedia Integration Language (SMIL, pronounced "smile"). SMIL 2.1 has the following design goals:

• Define an XML-based language that allows authors to write interactive multimedia presentations. Using SMIL, an author can describe the temporal behaviour of a multimedia presentation, associate hyperlinks with media objects and describe the layout of the presentation on a screen.
• Allow reusing of SMIL syntax and semantics in other XML-based languages, in particular those who need to represent timing and synchronization. For example, SMIL components are used for integrating timing into XHTML and into SVG.
• Extend the functionalities contained in the SMIL 2.0 into new or revised SMIL 2.1 modules.
• Define new SMIL 2.1 Mobile Profiles incorporating features useful within the mobile industry.