[Zope-dev] Zopinion : Wysiwyg and "reversible style sheets"

[Boris Borcic]

Martijn Faassen wrote:
> 
> Boris Borcic wrote:
> >
> > I've like many been keeping an eye on XML and XSLT. It
> > seems to me, that the high interest in these technologies
> > suffers from an astonishing blind spot : reversibility.
> [big snip]
> 
> I'm not sure if I get you here. I think reversing wysiwyg documents back
> into semantic content (XML) is very very hard, if not plain impossible.
> A different layout, especially with the current HTML table hacks, can
> really transform the way a document looks, and you'd need heuristics to
> make this work well at all; and heuristics don't always work.

Well, my idea would be to have appropriate html comments embedded into
the generated html, that would be preserved by the editor, and would
make the parsing of the modified document more deterministic. I don't
think a downsized version of such a facility would be as hard as you
say; but it certainly requires the expression logic (e.g. DTML or XSL)
to be designed from the start with such a facility in mind.

As a first step, one could concieve that the "rendering primitives",
translating an object to text, could tag their output with a machine-
-readable comment, indicating both the source object and the formatting
function that is "adjoint" (= the best reverse) to the one used to
render the object.

More thinking is required, when the matter comes to modifying aggregates,
e.g. adding or removing a row to a set produced by a looping construct;
but there again, the looping constructs could embed "reversibility
information" into html comments.

In any case, what I have in mind are *simple* layouts, intended for
such an usage. The user would be allowed to do wysiwyg editing, only
to the extend that the document's structure makes the intended change
clear. Again, the primitive example, is that of being able to change
the source of a mistaken digit by updating that digit in the output:
and the application should certainly be able to track such a digit
back to its source (I mean, I don't think this would require a true
miracle).

Reversible code is one of the beauties of logic programming... and
zope acquisition smacks of the rational trees of Prolog III... while
the request-by-request logic inherited from the HTTP protocol reminds
of prolog queries - especially as regards failures. I am wondering
if pushing this (admittedly vague) convergence can lead to further
treasures.

Boris Borcic