# XML parser **URL:** \ **Category:** Ruby\ **Created:** [July 19, 2008, 10:46pm UTC](https://www.ruby-forum.com/t/xml-parser/143516 "2008-07-19T22:46:57Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 19, 2008, 10:46pm UTC](https://www.ruby-forum.com/t/xml-parser/143516/1 "2008-07-19T22:46:57Z")
Hi guys, I’m looking for some information about the xml libraries available in Ruby. I’ve read a few blog post about the pro’s and con’s of REXML and Libxml but I still have some questions : - as I understand it REXML is part of ruby standard library and so is included in ruby distribution ? - libxml is a wrapper for gnome libxml and must be installed and compiled with gem ? - is libxml really a full validating and compliant parser ? - how do you use xslt in Ruby ? do you use [http://raa.ruby-lang.org/project/ruby-xslt/](http://raa.ruby-lang.org/project/ruby-xslt/) or [http://rubyforge.org/projects/libxsl/](http://rubyforge.org/projects/libxsl/) (if I’m right the second one is part of libxml ? ) As you see I’m lost and I would really appreciate your help or some comprehensive post about xml processing in ruby . Thanks ! Cedric ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 20, 2008, 12:45am UTC](https://www.ruby-forum.com/t/xml-parser/143516/2 "2008-07-20T00:45:45Z")
On Jul 19, 10:42 pm, Cédric H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > comprehensive post about xml processing in ruby . > > Thanks ! > > Cedric Parsing, manipulating XML is such wide subject. There is a more then one bookshelf full with books about it. Doing it with Ruby is not an exception. Beside these two libraries mentioned there is also an Hpricot (http:// [code.whytheluckystiff.net/hpricot/](http://code.whytheluckystiff.net/hpricot/)) and you should try it to. When dealing with XML you should consider the following questions: Who and on what OS the code will be running? How big the XML document is? Is the speed a decisive parameter? What’s the magnitude of manipulation required? Answers to these questions could help you pick the optimum library but you should be familiar with all of them. Do a research, play a little and pick the more appealing to you. ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 20, 2008, 2:40am UTC](https://www.ruby-forum.com/t/xml-parser/143516/3 "2008-07-20T02:40:59Z")
Cédric H. wrote: > I’m looking for some information about the xml libraries available in > Ruby. > > I’ve read a few blog post about the pro’s and con’s of REXML and > Libxml but I still have some questions : > > - as I understand it REXML is part of ruby standard library and so is > included in ruby distribution ? Yes. It’s also widely acknowledged as very slow. The RE stands for Regular Expressions, which are only fast when used carefully. Basing an entire parser on them tends to abuse them. This blog show how to spot-check compliance issues in the three leading Ruby XML parsers: > **[O'Reilly Media - Technology and Business Training](https://www.oreilly.com)** > > Gain technology and business knowledge and hone your skills with learning resources created and curated by O'Reilly's experts: live online training, video, books, our platform has content from 200+ of the world's best publishers. > - libxml is a wrapper for gnome libxml and must be installed and > compiled with gem ? Ordinarily, that process would be mostly harmless. You may already have libxml2-dev, if you have a GNU platform such as Ubuntu or CygWin. However, the current libxml-ruby has a nasty bug. First, it sprays lots of No definition for ruby\_xml\_parser\_context\_options\_get into the console. Then it refuses to install the libxml\_so.so file that it just created. I don’t know this bug’s status, but because my assert\_xpath works best with libxml, I must overcome it whenever we build a new workstation at work! Sometimes I must manually copy its executables into Ruby’s paths… (Our production code does not use libxml - only the test code.) I just tried to install while writing this post, and 0.8.1 might have worked on Ubuntu. > - is libxml really a full validating and compliant parser ? I suspect it’s the reference implementation for XML. It certainly takes every DOCTYPE and schema very seriously! Better, it actually forgives some errors and keeps working, unlike REXML > - how do you use xslt in Ruby ? do you use [http://raa.ruby-lang.org/project/ruby-xslt/](http://raa.ruby-lang.org/project/ruby-xslt/) > or [http://rubyforge.org/projects/libxsl/](http://rubyforge.org/projects/libxsl/) (if I’m right the second one > is part of libxml ? ) > > As you see I’m lost and I would really appreciate your help or some > comprehensive post about xml processing in ruby . Sorry! I was knocking 'em down, and you lost me at XSLT. In a pinch, I would pipe text thru xsltproc, and not worry about deep language integration. XSLT is nothing but a big filter, so I thought you could use it without making an object out of it. ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 20, 2008, 3:06am UTC](https://www.ruby-forum.com/t/xml-parser/143516/4 "2008-07-20T03:06:07Z")
> Beside these two libraries mentioned there is also an Hpricot (http:// > [code.whytheluckystiff.net/hpricot/](http://code.whytheluckystiff.net/hpricot/)) and you should try it to. Hpricot is a jack-of-all-trades-master-of-some-of-them. Don’t look to it for schema validation, XSLT, or true XPath. > When dealing with XML you should consider the following questions: > Who and on what OS the code will be running? > How big the XML document is? > Is the speed a decisive parameter? > What’s the magnitude of manipulation required? The two XML parser models are DOM and SAX. DOM converts every tag into an Object (hence Document Object Model), and lets you traverse the objects. The conversion is slow, and puts the entire document into memory, simultaneously. SAX lets you register callbacks to call when an XML reader encounters certain tags. It treats the input XML as a stream, hence zipping past nodes you don’t need is very fast. But I don’t know the Ruby SAX solution! ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 20, 2008, 5:23am UTC](https://www.ruby-forum.com/t/xml-parser/143516/5 "2008-07-20T05:23:34Z")
On Jul 19, 9:03 pm, Phillip O. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > hi, > > you may enjoy reading this! [http://www.rubyinside.com/ruby-xml-crisis-over-libxml-0-8-0-released-](http://www.rubyinside.com/ruby-xml-crisis-over-libxml-0-8-0-released-)… > (posted two days ago) FYI, Still some final fine-tuning going on, so don’t expect everything to be all roses just quite yet. But we are close, and might actually get to to a 1.0.0 release soon. T. ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 20, 2008, 3:09am UTC](https://www.ruby-forum.com/t/xml-parser/143516/6 "2008-07-20T03:09:38Z")
hi, you may enjoy reading this! [http://www.rubyinside.com/ruby-xml-crisis-over-libxml-0-8-0-released-955.html](http://www.rubyinside.com/ruby-xml-crisis-over-libxml-0-8-0-released-955.html) (posted two days ago) kind regards, phillip * * * Am 20.07.2008 um 02:34 schrieb Phlip: ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 21, 2008, 12:10am UTC](https://www.ruby-forum.com/t/xml-parser/143516/7 "2008-07-21T00:10:38Z")
Phlip wrote: > But I don’t know the Ruby SAX solution! REXML supports a “SAX Like” stream listening interface as well as DOM. See the REXML tutorial at [http://www.germane-software.com/software/rexml/docs/tutorial.html](http://www.germane-software.com/software/rexml/docs/tutorial.html), scroll down until you see the section headed with “Stream Parsing”. The upshot is you write a class that has callback methods (see [http://www.germane-software.com/software/rexml/doc/classes/REXML/StreamListener.html](http://www.germane-software.com/software/rexml/doc/classes/REXML/StreamListener.html) for a complete list of callbacks) and pass an instance of the class to REXML’s parse\_stream method. REXML also supports a SAX2 API, but I have never used it. Look for the heading “SAX2 Stream Parsing” in the tutorial link above. Recently converted a poor DOM based parsing solution to a stream listener based solution (not SAX2) and realized an order of magnitude improvement in performance. Saludos, -Doug ---
**Author:** ![CSSSSdric\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/f6c823/32.png) [@CSSSSdric\_H](https://www.ruby-forum.com/u/CSSSSdric_H)\ **Post date:** [July 20, 2008, 5:30am UTC](https://www.ruby-forum.com/t/xml-parser/143516/8 "2008-07-20T05:30:35Z")
Trans wrote: > > you may enjoy reading this! [http://www.rubyinside.com/ruby-xml-crisis-over-libxml-0-8-0-released-](http://www.rubyinside.com/ruby-xml-crisis-over-libxml-0-8-0-released-)… > > (posted two days ago) Tx - that’s why my install today worked, right? > FYI, Still some final fine-tuning going on, so don’t expect everything > to be all roses just quite yet. But we are close, and might actually > get to to a 1.0.0 release soon. And to use it with assert\_xpath you just gotta put invoke\_libxml in your setup…