Note

Date: Aug. 8, 1998
Link: http://www.w3.org/TR/NOTE-CSS-smil
Source Author or Organization: W3C

Excerpted from "Status of this Document" and "Introduction" sections: "Comments during the SMIL review period suggested that the relationship between SMIL and CSS should be more clearly explained. This note provides a detailed explanation of the relationship between SMIL layout and CSS. It updates a Note from June 15. Most changes are editorial. A section on mapping z-index values from SMIL basic layout to CSS has been added."

"SMIL basic layout has a few multimedia-related options that the initially text-based CSS does not cover yet. These will be submitted as requirements for work on CSS3."

" The SMIL basic layout language is an XML-based language that exposes parts of the W3C formatting model as defined by properties in the CSS2 recommendation. The majority of CSS2 properties only apply to text. Only a small number of the properties (7 out of 104) apply to multimedia."

" SMIL provides an XML-based syntax to interface with these properties rather than using CSS-syntax. The working group considered that is was too burdensome to require SMIL players to implement an additional parser for a CSS-based syntax when using such a small percentage of the CSS properties. However, SMIL allows the use of CSS2 as an alternate layout language, which allows a smooth upgrade to CSS2 in the future."

" SMIL is not the only W3C specification that exposes a subpart of the W3C formatting model, or uses a different syntax. Others are HTML 4.0 transitional, MathML and XSL [XSL]."

" In the following, we give the information required to build a SMIL renderer on top of a CSS2 implementation. Section 2 shows how the XML attributes used in SMIL basic layout are mapped into the syntax of CSS2 properties. Section 3 defines a fixed stylesheet that contains the values for all properties that are constant in SMIL basic layout, and different from the initial values defined in CSS2. Section 4 shows an example in which a SMIL document containing SMIL basic layout is converted into a document containing CSS2 which has the equivalent layout. Section 5 lists requirements for CSS3 that have been discovered during the work on SMIL."