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At 02:02 PM 3/5/2005, Bob Foster wrote:
>Andrew Jeavons wrote:
>>> From your description I'd guess that every verb/attribute combination
>>>and interaction has been hardcoded. If so, you might get the best
>>>bang for your buck by "acquiring" (training/hiring) someone who can
>>>help you re-write your existing XSLT.
>>Exactly. Which is totally brain dead. That's what set me on my search for
>>the BNF tool. Even with my minimal XSLT knowledge seeing the SAME code
>>over and over again made me very worried.....
>>The XSLT was done by external contractors, soon to be ex-contractors now
>>if I can help it. I know that I can make a parser out of Bison and Flex
>>with a fifth or less code
>>which will do far more than the XSLT does and be readable (well to me
>That's what you think you know, but it isn't correct in general. BNF can
>only do a surface syntax scan; you'll have to escape to a programming
>language to do any sort of semantic check. XSLT is far more powerful.
>That's not saying that the contractors' stylesheet actually uses any of
>this power, but it's there.
Reasonable point. Yes, BNF provides a validity checking mechanism but I
still have to write C/C++ or whatever to do anything concrete with the
elements I parse. And C et al
are not great languages for these kinds of job it is true.
>Plus, you seem to be missing this major point: Before you can teach your
>BNF to parse your XML application language, you first have to teach it to
>parse XML. This is a much bigger PITA than you imagine.
Yes and no. When I look at the XML language we have it is very (very)
simple, which is why I was aghast it taking 2666 lines of *ANYTHING* (XSLT,
C et al) to parse it. And also
looking at other systems I've written/worked on that use BNF parsers I'm
pretty certain it isn't a huge job. 20+ years of hacking code around...:-)
So while I accept your point
about XSLT being badly used in this case, I do know for an absolute fact I
can write a shorter parser in Bison, but it does seem clear now that the
problem isn't so much using
XSLT for the parsing as the way it has been done...
> The virtue of using existing schema languages is that they already know
> how to deal with the ins and outs of XML syntax, so you write grammars
> and rules at a much higher level than BNF.
Very true. What wasn't clear to me was that systems like XSLT could write
higher order grammars. This code was the first XSLT I had seriously looked
at and it didn't give a good
>As a parser-aware person, you should find RELAX NG compact syntax easy to
>understand and able to express what you need. If there is something you
>can't say, you can add Schematron assertions to the same schema. I'd
>strongly recommend you check it out.
Thanks, I'll check it out, I appreciate the comments/information.
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