Re: [greenstone-users] ranking order

From Katherine Don
DateFri, 10 Dec 2004 11:10:32 +1300
Subject Re: [greenstone-users] ranking order
In-Reply-To (fc-00664147002ab12b00664147002ab12b-2ab148-campus-clacso-edu-ar)
Hi Dominique

Search results are ranked if you do a "some" search and not if you do an
"all" search. For searching multiple collections, if you do an all
search, then you get the behaviour you describe. But if you do a some
search, then documents *are* ranked. Ranks from each collection are
taken at face value, and the documents ordered by these ranks. This is
not all that good, as ranks from different collections may not correspond.

To do it properly, you would need to query each collection for the
frequency of each query term, to calculate the total frequency over all
the collections. From this you can calculate weights for each query
term, which you then need to pass in when you do the query. This way the
ranks will be accurate.

We have never gotten around to implementing this, and have just hoped
that doing it the easy way was good enough.

I hope this helps,
Katherine Don

Dominique Babini wrote:
> We observe that the ranking of search results is organized by collection
> and, within each collection, it is not ranked by frequency of term
> requested. As we have many collections, and a search facility to search
> in "all collections", how can we do so that the results be a ranking by
> frequency of term requested and considering all collections together?.
> We appreciate any help,
> Dominique
> our virtual library in demo is in
> Dra. Dominique Babini
> Coordinadora Area Informaci?n
> Consejo Latinoamericano de Ciencias Sociales - CLACSO
> Biblioteca Virtual de Ciencias Sociales de Am?rica Latina
> y el Caribe de la red de centros miembros de CLACSO
> Av. Callao 875, 3ro. E
> (C1023 AAB) Buenos Aires, Argentina
> Tel.: (54-11) 4814-2301/4811-6588
> Fax: (54-11) 4812-8459
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