Re: [Fwd: Re: Language is not markup and markup is not language.]

[Paul Prescod <paul@xxxxxxxxxxx>]

James Clark wrote:
> 
> You can use a string that separates the representation of each location
> by some delimiter (say a /); then you can use basic arithmetic,
> recursion and substring-before/substring-after to index to a particular
> location.

There goes that argument! I guess I'm not Guy's hero anymore. Oh well,
I'll get over it.

As I admitted a few messages ago, XSL was sufficiently complex that the
question of Turing completeness was probably academic. The types of
guarantees and optimizations allowed by global code analysis would be too
hard anyway.

> If an optimization would be possible except for some new
> feature in XSLT, you don't have to completely give up on that
> optimization, rather you can analyze the stylesheet to determine whether
> it makes use of that feature and then only apply the optimization if the
> stylesheet does not make use of the feature.

Sometimes that will be feasible and sometimes it will not. It's one of
those things that is easier said than done because it can lead to really
hairy code. What if there are five global optimizations that can be turned
on or off based on features in the stylesheet? There are 5! combinations
of them which means that you have to think very carefully about how they
relate to each other.

"With a sufficiently sophisticated compiler I could move the world."

-- 
 Paul Prescod  - ISOGEN Consulting Engineer speaking for only himself
 http://itrc.uwaterloo.ca/~papresco

Diplomatic term: "Emerging Markets"
Translation: Poor countries. The great euphemism of the Asian financial
             meltdown. Investors got much more excited when they thought 
they could invest in up-and-comers than when they heard they could invest 
in the Third World.(Brills Content, Apr. 1999)


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