The W3C's Behavioral Extensions to CSS (BECSS) Working Draft has inspired discussion on transformations, normally the domain of XSL, and Cascading Style Sheets on the www-style mailing list.

BECSS is a draft document describing mechanisms for assigning behavior (like HTML mouseovers) through CSS style sheets, replacing what had been the work of HTML attributes with CSS properties. It provides for the inclusion of 'script blocks' within style sheets, and describes "HTML components" that use HTML and XML as foundations for describing behaviors. These HTML components may be referenced by style sheets.

Sjoerd Visscher started the "CSS-Tranformation mechanism and modularizing CSS" discussion by proposing a simple mechanism for adding content to documents through CSS. Bert Bos pointed out Simple Tree Transformation Sheets 3 (STTS3), a proposal written by one of the authors of the BECSS document. Chris Wilson brought up the distinction between 'decoration', traditionally the task of CSS, and 'transformation'. He noted that the Document Object Model (DOM) Level 2 Working Draft, currently in Last Call, omits discussion of those parts of CSS2 which could be considered 'transformative', like the :before and :after pseudo-attributes. Chris Lilley suggested making some of this tree-representation the work of DOM Level 3, which hasn't (publicly, anyway) started yet.

More recently, Sjoerd Visscher has expanded his example, proposing extensions to BECSS for providing attribute values. Ian Hickson presented a description of CSS and DOM interactions that suggested incompatibility, and the discussion continues.

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