[ http://issues.apache.org/jira/browse/NUTCH-134?page=all ]
Jerome Charron updated NUTCH-134:
---------------------------------
Attachment: summarizer.060506.patch
Here is a patch that add a summarizer extension point and two summarizer
plugins : summarizer-basic (the current nutch implementation) and
summarizer-lucene (the lucene highlighter implementation).
Please notice that the lucene plugin is a very crude implementation : the
highlighter directly constructs a text representation of the summary, so we
need to parse the text to build a Summary object!!! (improvements are welcome).
This is a first step to this issue resolution.
If no objection, I will commit this patch in the next few days and then:
1. Fix in the summarizer-basic the original issue reported by Andrzej
2. Add a toString(Encoder, Formatter) method in Summarizer so that a Summary
object could be encoded and formatted with many implementations (it is the same
logic as the one in Lucene Highlight) - Andrzej, do you prefer this solution or
a solution where Summary is Writable?
PS: Chris, sorry but the major part of this patch was already done when you
added your comment.
> Summarizer doesn't select the best snippets
> -------------------------------------------
>
> Key: NUTCH-134
> URL: http://issues.apache.org/jira/browse/NUTCH-134
> Project: Nutch
> Type: Bug
> Components: searcher
> Versions: 0.7.2, 0.7.1, 0.7, 0.8-dev
> Reporter: Andrzej Bialecki
> Attachments: summarizer.060506.patch
>
> Summarizer.java tries to select the best fragments from the input text, where
> the frequency of query terms is the highest. However, the logic in line 223
> is flawed in that the excerptSet.add() operation will add new excerpts only
> if they are not already present - the test is performed using the Comparator
> that compares only the numUniqueTokens. This means that if there are two or
> more excerpts, which score equally high, only the first of them will be
> retained, and the rest of equally-scoring excerpts will be discarded, in
> favor of other excerpts (possibly lower scoring).
> To fix this the Set should be replaced with a List + a sort operation. To
> keep the relative position of excerpts in the original order the Excerpt
> class should be extended with an "int order" field, and the collected
> excerpts should be sorted in that order prior to adding them to the summary.
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