Re: [greenstone-devel] re Sort order of search result list and browse list

From Katherine Don
DateMon, 19 Jun 2006 12:00:25 +1200
Subject Re: [greenstone-devel] re Sort order of search result list and browse list
In-Reply-To (44922096-1020105-cs-waikato-ac-nz)
Hi

MG does either boolean or ranked queries (but not both at once) while
MGPP ranks boolean queries. So the "display results in ranked/natural
order" just switches the ranking on/off.
Only documents which match the boolean query will be included in the
results.

The ranking is done using a cosine measure (based on term frequency,
document frequency, document weights...) - see the book mentioned below
for more information about this.

There is a website about MG, at http://www.cs.mu.oz.au/mg/ and there is
a link there to more information about the software. I thought it may
have info about the ranking, but it is down at the moment. I'm not sure
if this is a permanent error, so you may like to check there.

MGPP is a reimplementation of MG which is written in C++ instead of C,
and uses word level indexing instead of document level. I think that the
compression, indexing and ranking algorithms are pretty much the same as
for MG.

Regards,
Katherine


Michael Dewsnip wrote:
> Hi,
>
> The best source of information about the ranking done by MG (and MGPP,
> which is similar) is the "Managing Gigabytes" book, by Ian H. Witten,
> Alistair Moffat and Tim Bell.
>
> If you're technically inclined the cheap version is to look at the code
> and its comments :-)
>
> Regards,
>
> Michael
>
>
>
> Ying-Hsang Liu wrote:
>
>
>>Hello,
>>
>>I am using Greenstone for an information retrieval experiment. After
>>consulting
>>Greenstone documentation and the following message, it is still not
>>clear to me
>>how the ranking works in Greenstone (I am using version 2.70),
>>specifically
>>MGPP search engine.
>>
>>My collection is built upon MGPP. If I search the system using
>>advanced form
>>search and choose the option "Search and display results in ranked
>>order," how
>>does the system work?
>>
>>Is it a Boolean-based search with ranked output? Or, is it a ranked
>>query, like
>>the "Some" option search in simple form search? If either one involves
>>the ranking
>>of search results, could I get more detailed descriptions in technical
>>reports or
>>published papers?
>>
>>Thanks,
>>
>>
>>Ying-Hsang Liu
>>
>>--
>>PhD Student
>>Rutgers - The State University
>>School of Communication,
>>Information and Library Studies
>>4 Huntington St.
>>New Brunswick, NJ 08901
>>USA
>>
>>
>>
>>
>>
>>*Michael Dewsnip* mdewsnip at cs.waikato.ac.nz
>><mailto:greenstone-devel%40list.scms.waikato.ac.nz?Subject=%5Bgreenstone-devel%5D%20re%20Sort%20order%20of%20search%20result%20list%20and%20browse%0A%09%20list&In-Reply-To=>
>>/Fri Sep 26 11:39:51 NZST 2003/
>>
>> * Previous message: [greenstone-devel] re Sort order of search
>> result list and browse list
>> <https://list.scms.waikato.ac.nz/mailman/htdig/greenstone-devel/2003-September/000238.html>
>> * Next message: [greenstone-devel] re Sort order of search result
>> list and browse list
>> <https://list.scms.waikato.ac.nz/mailman/htdig/greenstone-devel/2003-September/000241.html>
>> * *Messages sorted by:* [ date ]
>> <https://list.scms.waikato.ac.nz/mailman/htdig/greenstone-devel/2003-September/date.html#239>
>> [ thread ]
>> <https://list.scms.waikato.ac.nz/mailman/htdig/greenstone-devel/2003-September/thread.html#239>
>> [ subject ]
>> <https://list.scms.waikato.ac.nz/mailman/htdig/greenstone-devel/2003-September/subject.html#239>
>> [ author ]
>> <https://list.scms.waikato.ac.nz/mailman/htdig/greenstone-devel/2003-September/author.html#239>
>>
>>
>>Hi Stephen,
>>
>>Thanks very much for your answer.
>>
>>In regards to the ordering of the search results, it depends on whether a
>>boolean or ranked query is being performed. For a ranked query the search
>>results are ordered according to how closely they match the query (as you
>>would expect). For a boolean query, a document either matches or
>>doesn't, so
>>there is no scope for ordering. Therefore, the documents are simply listed
>>based on the order they were indexed by MG/MGPP, as you guessed.
>>
>>Regards,
>>
>>Michael
>>
>>------------------------------------------------------------------------
>>
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>>greenstone-devel mailing list
>>greenstone-devel@list.scms.waikato.ac.nz
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>>
>>
>
>
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