XSLT is really separating (XML) data from markup in the case of the web. More generally it's transforming between different XML formats. But in the case of doc

XSLT is really separating (XML) data from markup in the case of the web. More generally it's transforming between different XML formats. But in the case of docs (eg XML-FO for docbook, DITA etc) XSLT does actually separate content from styling.