Re: [Docutils-develop] math directive issues

[G. M. <mi...@us...>]

On 14.05.08, David Goodger wrote:
> On Wed, May 14, 2008 at 1:38 PM, Alan Isaac <ai...@am...> wrote:

> I don't think that a Writer should handle unrecognized formats.
> Recognizing formats and dealing with input is the job of a Parser or
> Reader. A Writer's job is to convert a standard doctree to the output
> format.

> Yes, I realize that this is dealing with a distinct data format, so
> the model may break down. But this is something to keep in mind.

We should care to differentiate between *input*, *internal*, and *output*
format.

The basic question for inclusion of a math-directive is "How should the
standard doctree store the content of a math node?" I. e. which
*internal* format should docutils use.

The set of supported input and output formats can be extended later
without change to the doctree specification.

IMO, the main candidates for the *internal* data format are:

LaTeX
  best graphical representation, relatively simply to type in directly,
  widely supported and established in the scientific community.

Math-ML 
  modern data-exchange format, standardised, "the future", 
  hard to type in by hand.

Unfortunately, conversion between them is not always loss-less, so it is
desirable to keep input data that is in one of them in this format if
the *output* data requires the same.

> Math processing [...] should be handled [...] in a Transform. Even if
> the output depends on the type of Writer, a Transform is the way to go.

IMO, the Transform should convert the *input* format into the *internal*
format (the one required by the current writer or both), normalising the
doctree.

Jens' latex-math provides the code for a LaTeX->MathML Transform, 
searching for a suitable MathML-LaTeX converter is the next important
step.

> By the time the Writer sees it, the math should be just a blob to
> insert into the output stream.

In the most basic cases, yes. But generally a writer will convert the
*internal* format of the standard doctree to the *output* format.

* the html+mathml writer just inserts the Math ML,

* the latex writer inserts LaTeX code.

However, some html writer variants (or options) would care for older
browsers not understanding Math-ML

* "html+pngmath" would produce graphical representations of the
  formulae from the LaTeX data (a la latex2html),
  
* "html+htmlmath" would convert the Math-ML to a HTML+CSS
  substitution,

* "html-jsmath" would write HTML+java-script for the jsmath extension...

Other writers are feasible as well, e.g. 

* a "unicode" writer could convert the math node content to a textual
  representation using the Unicode chars for math symbols. 
  
  (Unicode defines "all possible" mathematical symbols, using a
  fixed-width font, even large symbols (spanning multiple lines) can be
  constructed.)

Günter