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Transformation + FOs makes abuse easy

Subject: Transformation + FOs makes abuse easy
From: "Simon St.Laurent" <simonstl@xxxxxxxxxxxx>
Date: Wed, 28 Apr 1999 12:54:17 -0400
transformation vocabulary
'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
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 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list

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