[xml] parser/tokenizer [was Re: support for xml schema in libxml2]



On Tuesday 04 July 2006 16:32, Buchcik, Kasimier wrote:
Hi,

-----Original Message-----
From: xml-bounces gnome org [mailto:xml-bounces gnome org] On
Behalf Of boss gregerhaga net

[...]

I'd like to help. Quite honestly:I have very little knowledge of the
big picture about XML, XSLT and related technologies. I have used
libxml2 recently, see my site
http://www.gregerhaga.net/qxrss-1.2.6-dox for my rss reader, which
uses it ( perhaps in a stupid way but still*grin*).

So:what can i do to contribute? What is the learning curve
like for an almost newbie in XML but with experience from C?

Greger

I'll list the things I would do, when I would be about to
put the rope around my neck - as you do (hmm, we _are_ scary):

1) A good starter for XML stuff is http://www.w3schools.com/
  Besides other things, it teaches (rudimentally) about XSLT 2.0,
  XQuery 1.0 and XPath 2.0.

2) Google around for some deeper tutorials, articles, etc.; but don't
  get lost, since it might become boring.

3) Read the specs: http://www.w3.org/Style/XSL/ ; but again, don't get
  lost, since it might become boring and we'll never see you again.

4) Get in touch with Libxml2's XPath code. Write an XPath test app and
  debugg the parser and evaluation code, while switching back and
  fro to the specs (XPath 1.0 in this case) and trying to understand
  why the code does what it does. Write down the obervations, new ideas,
  things you would have done differently, etc. Maybe, just for learning,
  also add a piece of self-invented syntax to the XPath machinery, in
  order to get a feeling how to change/extend things without breaking
them.

5) I think one will need to create a scenario for oneself, where
  one actually _needs_ to implement XPath 2.0/XQuery 1.0/XSLT 2.0.
  This can either be the fact that you already told all your
girl-friends
  that you're gonna do it (this might be not enough a reason), some
  idealistic reasons, some business-related issues, etc.

6) Wear heavy chains for about 2 weeks, then buy some t-shirts with
  XPath 2.0/XQuery 1.0/XSLT 2.0 written on it in fancy letters.

7) Try to annoy people with questions, bugzilla-entries, etc.
   See http://www.xmlsoft.org/bugs.html

But I don't know how to actually start writing such new code. Daniel
will have to tell us (or at least me) what he expects; I would need to
know to what extent new code for XPath 2.0 can be written and what
existing code should be rather extended; so questions like:
- Should the existing expression-parsing code be extended (is this
  possible?), or should we write on new one for XPath 2.0?

One could consider Bison combined with a hand written tokenizer(that's how 
Patternist do it). Here's an XQuery grammar; path expressions and (some) XML 
literals are missing, but other than that it's quite complete:

http://websvn.kde.org/trunk/kdenonbeta/kdom/patternist/parser/QueryTransformParser.ypp?rev=557332&view=log

The tokenizer is in the same dir, but I doubt it would be useful.

[...]
Finally, I think that there's no need not know much about
XML-related technology to be able to code much stuff for e.g. the
XPath 2.0 module.

Grasping the specs can be daunting. It was that for me. And is..


Cheers,

                Frans



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