Re: Why Core Flow Objects

[Paul Prescod <papresco@xxxxxxxxxxxxxxxx>]

Francois Belanger wrote:

> ... 
> If the second rule is valid (I think it is), then one can create any kind
> of output using CDATA sections and do away with Core Flow Objects.
> 
> Is this a good approach? Or is it the equivalent of the one-pixel GIF
> hack in HTML and defeats the purpose of XSL?

The "HTML Flow Objects" are a temporary (though perhaps long-lived)
hack. One of the nasty things about them is that they confuse people
into thinking that XSL transforms one text string (an XML document) into
another (an HTML document). It does not:

 * A parser transforms an XML document into a grove or "document object"
 * XSL transforms that into a "flow object tree"
 * A browser or word processor displays the flow object tree.

An actual HTML file never conceptually exists, not even as a stream of
bytes in memory. If that HTML file existed, and could contain any text
at all, (as you propose) then it would have to be parsed, which would
slow everything down.

Now a particular implementation (like docproc or msxml) might decide to
allow you get access to an HTML file that *represents* the flow object
tree, but that doesn't mean that XSL itself defines a conversion from
XML into HTML. It does not.

> I see it as a barrier to adoption more than
> anything else as one has to wait for Core Flow Object to be available and
> supported by a parser to generate different file formats from XML.

This is your conceptual problem. XSL does not exist to "generate
different file formats." It is a stylesheet language for applying style
(formatting!) to XML documents. Thought of in that way, the reasons for
the current choices are probably clear.

 Paul Prescod  - http://itrc.uwaterloo.ca/~papresco

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