Re: What will be the future improvements of XSLT?

["Oren Ben-Kiki" <oren@xxxxxxxxxxxxx>]

Miloslav Nic <nicmila@xxxxxxxx> wrote:
> If reuse of result trees was possible, 90% off my problems and ugly
> hacks would disappear. I would really appreciate to know the rationale
> why the spec says what is says (implementation problems?)

This was discussed in this mailing list; the main reason given was that by
limiting XSLT to a "single pass" it would be easier to implement
"incremental" XSLT processors. Such processors are deemed important for
editors etc. I don't know whether this was in fact the main reason for it -
and we wouldn't know unless some WG member confirms it.

I personally don't buy this reason because (i) even a single pass
incremental XSLT processor is very hard to do and (ii) even with the current
restricted spec it is possible to write a multi-pass stylesheet. In fact
XSLT has hit the Turing-complete limit and attempts to justify all sort of
restrictions in order to allow "automatic reasoning" of various types on it
are pretty much futile. This is not to say that incremental processors or
other form of automatic reasoning on XSLT stylesheets would not be available
in practice; it is just that such tools would by necessity be limited to
"simple enough" stylesheets.

BTW, I do accept the reasoning behind immutable variables - they make it
possible to write very efficient parallel implementations of XSLT
processors, and if incremental XSLT processing is ever done, immutable
variables will help a lot.

Have fun,

    Oren Ben-Kiki


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