Custom Tokenizer not working

on 23.04.2008 20:00

[unfortunately I received my messages as a batched digest...hence, I'm
forced to respond in a new thread. I've requested the administrator to
change my config to receive each message on this list. Sorry for any
inconvenience]

Thanks for the response below. Here is XMLAnalyzer (currently I'm not 
using
the stop or lower case filter):

  class XMLAnalyzer < Ferret::Analysis::Analyzer
    def initialize(synonym_engine = nil,
                   stop_words = FULL_ENGLISH_STOP_WORDS,
                   lower = true)
      @synonym_engine = synonym_engine
      @lower = lower
      @stop_words = stop_words
    end

    def token_stream(field, str)
      # ts = XMLTokenizer.new(str)
      ts = StandardTokenizer.new(str)
      # test_token_stream(ts)
      return ts
    end

  end

I just tried running ferret-browser by pointing to an index created with
StandardTokenizer and got the  error below in Firefox. Is there any
configuration that is necessary? Presumably the defaults should work.

John

Internal Server Error No such file or directory -
/usr/local/lib/site_ruby/1.8/ferret/browser/views/error/index.rhtml
------------------------------
 WEBrick/1.3.1 (Ruby/1.8.6/2007-06-07) at 127.0.0.1:3301

Hi!

On Wed, Apr 23, 2008 at 12:18:12PM -0400, S D wrote:
[..]
>* My current problem, a custom tokenizer I've written in Ruby does not
*>* properly create an index (or at least searches on the index don't 
work).
*>* Using test_token_stream() I have verified that my tokenizer properly 
creates
*>* the token_stream; certainly each Token's attributes are set 
properly.
*>* Nevertheless, simple searches return zero results.
*
Could you have a look at your index with the ferret_browser utility? It
allows you to check what exactly has been indexed and that maybe leads
to the root of your problem.

What does your analyzer, where you use the Tokenizer, look like? Is your
next() method below being called and working correctly when test driving
your analyzer i.e. in irb?

Cheers,
Jens

>* The essence of my tokenizer is to skip beyond XML tags in a file and break
*>* up and return text components as tokens. I use this approach as 
opposed to
*>* an Hpricot approach because I need to keep track of the location of 
the text
*>* with respect to XML tags since after a search for a phrase I'll want 
to
*>* extract the nearby XML tags as they contain important context. My 
tokenizer
*>* (XMLTokenizer) contains a the obligatory initialize, next and text 
methods
*>* (shown below) as well as a lot of parsing methods that are called at 
the top
*>* level by the method XMLTokenizer.get_next_token which is the primary 
action
*>* within next. I didn't add the details of get_next_token as I'm 
assuming that
*>* if each token produced by get_next_token has the proper attributes 
then it
*>* shouldn't be the cause of the problem. What more should I be looking 
for?
*>* I've been looking for a custom tokenizer written in Ruby to model 
after; any
*>* suggestions?
*>*
*>*     def initialize(xmlText)
*>*       @xmlText = xmlText.gsub(/[;,!]/, ' ')
*>*       @currPtr = 0
*>*       @currWordStart = nil
*>*       @currTextStart = 0
*>*       @nextTagStart = 0
*>*       @startOfTextRegion = 0
*>*
*>*       @currTextStart = \
*>*         XMLTokenizer.skip_beyond_current_tag(@currPtr, @xmlText)
*>*       @nextTagStart = \
*>*         XMLTokenizer.skip_beyond_current_text(@currTextStart, 
@xmlText)
*>*       @currPtr = @currTextStart
*>*       @startOfTextRegion = 1
*>*     end
*>*
*>*     def next
*>*       tkn = get_next_token
*>*       if tkn != nil
*>*         puts "%5d |%4d |%5d   | %s" % [tkn.start, tkn.end, 
tkn.pos_inc,
*>* tkn.text]
*>*       end
*>*       return tkn
*>*     end
*>*
*>*     def text=(text)
*>*       initialize(text)
*>*       @xmlText
*>*     end
*>*
*>* Below is text from a previous, related message that shows that 
StopFiltering
*>* is not working:
*>*
*>* >* I've written a tokenizer/analyzer that parses a file extracting
tokens and
*>* *>* operate this analyzer/tokenizer on ASCII data consisting of
XML files (the
*>* *>* tokenizer skips over XML elements but maintains relative
positioning). I've
*>* *>* written many units tests to check the produced token stream and 
was
*>* *>* confident that the tokenizer was working properly. Then I 
noticed two
*>* *>* problems:
*>* *>*
*>* *>*    1. StopFilter (using English stop words) does not properly 
filter the
*>* *>*    token stream output from my tokenizer. If I explicitly pass 
an
*>* array of stop
*>* *>*    words to the stop filter it still doesn't work. If I simply 
switch my
*>* *>*    tokenizer to a StandardTokenizer the stop words are
*>* appropriately filtered
*>* *>*    (of course the XML tags are treated differently).
*>* *>
*>* >*    2. When I try a simple search no results come up. I can see 
that my
*>* *>*    tokenizer is adding files to the index but a simple search 
(using
*>* *>*    Ferret::Index::Index.search_each) produces no results.
*>* *
*>*
*>*
*>* Any suggestions are appreciated.
*>*
*>* John
*
>* _______________________________________________
*>* Ferret-talk mailing list
*>* Ferret-talk at rubyforge.org
<http://rubyforge.org/mailman/listinfo/ferret-talk>
*>* http://rubyforge.org/mailman/listinfo/ferret-talk
*

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