The first W3C Working Group on Synchronized Multimedia (SYMM) developed SMIL - Synchronized Multimedia Integration Language. This XML-based language is used to express synchronization relationships among media elements. SMIL 1.0 documents describe multimedia presentations that can be played in SMIL-conformant viewers.
SMIL 1.0 did not define a Document Object Model. Because SMIL is XML based, the basic functionality defined by the Core DOM is available. However, just as HTML and CSS have defined DOM interfaces to make it easier to manipulate these document types, there is a need to define a specific DOM interface for SMIL functionality. The current SYMM charter includes a deliverable for a SMIL-specific DOM to address this need, and this document specifies the SMIL DOM interfaces.
Broadly defined, the SMIL DOM is an Application Programming Interface (API) for SMIL documents and XML/HTML documents that integrate SMIL functionality. It defines the logical structure of documents and the way a document is accessed and manipulated. This is described more completely in "What is the Document Object Model".
The SMIL DOM will be based upon the DOM Core functionality (see DOM Core: The SMIL DOM Foundation). This describes a set of objects and interfaces for accessing and manipulating document objects. The SMIL DOM will also require the additional event interfaces described in the DOM Level 2 Events module. The SMIL DOM extends these interfaces to describe elements, attributes, methods and events specific to SMIL functionality.
Note that the SMIL DOM does not require support for DOM Level 2 Views, Stylesheets, CSS, Traversal, and Model Range modules.
The SYMM Working Group is also working towards a modularization of SMIL functionality, to better support integration with HTML and XML applications. Accordingly, the SMIL DOM is defined in terms of the SMIL modules.