Re: Application Design

[Francis Norton <francis@redrice.com>]

Sean McGrath wrote:
> 
> James Clark himself has been known to post to this list about the application
> areas where XSL is probably not the right way to go:
> 
While I agree with both the comments quoted, I would point out that the
editors of the XSLT spec weren't infallible, and if anything tended to
err on the side of being over-conservative about scope. For example,
restricting RTFs (Result Tree Fragment, the data type mainly returned by
complex operations) so that it could only be processed as a string, not
as a XML sub-tree, turns out to have been fairly gratuitous.
> 
> 
> Summary:
> 
> XSLT has its uses but it is surprisingly useless in some
> common server-side scenarios.
> 
We have found it fairly effective, though the lack of debuggers has been
a nuisance. There is a learning process, but everyone using XML needs to
learn XPath anyway (*please* don't tell me anyone is seriously
programming complex transformations by using pure DOM navigation) and
once you've go that, the rest of XSLT isn't that indigestible -
certainly no more of a leap than going from sequential to event-based
programming. 

> XSLT gets complicated quickly. The side-effect free nature
> of its processing model causes much pain for developers.
> The theoretical reason for this - parallelization of execution
> of the stylesheet - seems to me to be unjustified. It puts too
> much complexity on the programmers plate for what is after
> all an optimisation feature.
> 
Some bits are complicated, especially to do with grouping and loops. But
if people couldn't cope with declarative stuff neither SQL nor regular
expressions would have taken off. I can still remember people telling me
how complicated SQL was to learn. As Keynes said (more or less), today's
common sense is just yesterday's theories.

> Arguments against the "just use XSLT" mantra, including this
> one, will be pooh poohed by vendors who know full
> well what the limitations are but see lots of $$$ in
> debuggers, visual tools, consulting etc. etc.
> 
I suspect that most popular programming language more complicated than
DOS batch language have an IDE or two, and a user base split between
those who understand the fundamentals and those who just know how to use
the IDE.

Francis.