Transformation + FOs makes abuse easy
'Abuse' - the delivery of information locked into a particular presentation-oriented format, from which the original semantics are difficult to derive, is possible with both XSL and CSS. However, the structure of CSS is designed to keep those semantics (indeed, the entire document structure) intact, while the structure of XSL is designed to transform semantics into presentation. Cascading Style Sheets' focus on external style sheets providing supplementary formatting information to documents allows developers to assign presentation information to elements based on information (like their element name, or the value of a class attribute) that typically represents element meaning. The original document structure is always transmitted, along with the style sheet - there is no transformation to a 'pure' presentation vocabulary until the final stage of rendering. Extensible Style Language similarly focuses on external style sheets, but these style sheets tell programs how to transform documents from one vocabulary to another. This transformation process provides powerful tools for converting and rearranging documents. In addition to defining the transformation vocabulary, XSLT, XSL also defines a presentation vocabulary, called formatting objects (FOs). Formatting objects contain no semantic information, apart from the conventions designers have traditionally used to convey information to human readers. While the end result of both of these style tools may in fact look identical within a browser frame or on paper, the underlying information is quite different. In the CSS version, the original semantics are always available to the recipient, and the information can be easily reused in other processors. In the XSL version, the final product is useful only to a human reader after the transformation has taken place. The original proposals behind XSL seem to have intended that transformation and presentation go together, and that formatting objects would exist only inside of rendering software. The growing separation between the transformation tools (which have uses beyond FOs) and the formatting vocabulary (which is now another XML application) has created a very real possibility that organizations will choose to send their XSL-processed information to browsers using the FO vocabulary or presentation-oriented HTML. At this point, the use of transformations can keep 'meaningful' XML off the Web. As a result, the 'meaningful Web' project that was the driving force (at least in public) for the creation of XML is at risk. Server-side transformation from semantically rich private vocabularies to presentation-oriented public vocabularies may leave the Web exactly where it was before - interesting to read, but not very useful. Simon St.Laurent XML: A Primer Sharing Bandwidth / Cookies http://www.simonstl.com XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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