Subject: Re: Style vs. transformation From: "Frank Boumphrey" <bckman@xxxxxxxxxxxxx> Date: Wed, 4 Mar 1998 12:05:44 -0800 |
>>If I implemented XSL with Python as its expression language would I be cast into utter darkness...<< No, but isn't XSL meant to be for the HTML crowd, 98% of whom know something about Javascript, and 1% of whom know about Python? My understanding is that XSL was implemented because DSSSL-0 was too complicated for the average web author. Frank -----Original Message----- From: Sean Mc Grath <digitome@xxxxxx> To: xsl-list@xxxxxxxxxxxxxxxx <xsl-list@xxxxxxxxxxxxxxxx> Date: Wednesday, March 04, 1998 3:43 AM Subject: Re: Style vs. transformation >[Paul Prescod] >> >>The style language is demonstrably a transformation. It takes input and >>transforms it into output. It is also demonstrably a *complete* >>transformation: any transformation that can be expressed in any other >>transformation language can be expressed in the style language. It is >>also a *good* transformation language. For SGML->SGML transformations, I >>use the DSSSL style language variant available in Jade over any other >>transformation language. > >I have some in the trenches experience of this that lead me to >the conclusion that separate tree transformation and tree formatting >is more trouble than it is worth. > >Executive Summary : I agree with Paul Prescod > >Details: > >In developing the IDM SGML transformation system, >we started out with the idea of developing DTDs to >encapsulate the capabilities of any rendered output format. >We created DTDs for Winhelp, Folio, Motes, RTF, MIF etc. > >>From there, we reasoned, we had a straight tree transformation >task and no need for a style language. Fine in theory, horrible >in practice. The complexity of expressing the tree transformation >from say Docbook DTD to Winhelp DTD is just terrible. > >So we introduced a style language. The style language allowed >us to say: > NewParagaph() > AddToLeftIndent ("512") > BoldOn() > AddText ("Hello World") > >Behind the scences, this was just syntactic sugar for a tree >creation process. Then we had an epiphany - why not just say:- > > StartElement ("PARA") > AddAttribute ("LeftIndent","512") > AddAttribute ("Bold","1") > AddDataNode ("Hello World") > EndElement ("PARA") > >The achieves the same effect but uses a Style Langauge as a general >purpose SGML -> SGML transformation. After three years of >interative development of this stuff we now have a style >language (Python) and a collection of DTDS. >To target Winhelp, we create flow objects from the Winhelp >DTD. A simple back-end conversion then converts from there >to native Winhelp RTF. > >Most of the tree transformation code we wrote has >fallen into disuse as more and more gets achieved >in the style language. > >In defense of a Tree Transformation approach, it does >lead to good problem decomposition and code reuse. >You break a complex transformation down into a collection >of intermediate stages (we called them deltas) and the >entire transformation is achieved by "piping" them together >Unix style. > >I would like to see something in XSL that supported >"chaining" the flow object tree resulting from one >stylesheet transformation into another stylesheet. > >On a slightly related note, by far the biggest headache >we have to deal with in doing SGML/XML formatting is dealing >with document *collections*. We have found that our >style language invariable needs meta-data about the >document collection to generate the desired output. >This ranges from simple "next/previous document" metadata >for document chaining via hypertext through to running >headers for non-scrolling regions and so on. > >Is there anything the works for XSL that would support >this sort of thing? Allowing a stylesheet access to >command line paramaters would be a good start. > >Finally, finally. A curved ball. Is XSL inextricably >linked to JavaScript as it scripting environment? >If I implemented XSL with Python as its expression >language would I be cast into utter darkness... > >Sean > > > XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list > XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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