On Thu, Jan 29, 2009 at 12:38 PM, Teodor Sigaev
<teodor@sigaev.ru> wrote:
Is this what is desired? It seems to me that Wdoc is getting a high
ranking even when we are not sure of the position information.
For a cover of 2 query items, 0.1 is actually the maximum rank. This is only possible when both query items are adjacent to each other.
0.1 may not seem too high when we look at its absoule value. But the problem is we are ranking a document for which we have no positional information available higher than a document for which we may have positional information available with let suppose the cover length of 3. I think we should rank the document with cover length 3 higher than the document for which we have no positional information (and assume cover length of 2 as we are doing now).
I feel that if ext.p=ext.q for query items > 1, then we should not count that cover for ranking at all. Or, another option will be to significantly inflate nNoise in this scenrio to say 100. Putting nNoise=(ext.end-ext.begin)/2 is way too low for covers that we have no idea on (it is 0 for query items = 2).
I am not assuming or suggesting that rank_cd is bounded by one. Off course its rank increases as more and more covers are added.
Thanks,
Sushant.
The comment above says that "In this case we approximate number of
noise word as half cover's length". But we do not know the cover's
length in this case as ext.p and ext.q are both unreliable. And ext.end
-ext.begin is not the "cover's length". It is the number of query items
found in the cover.
--
Teodor Sigaev E-mail: teodor@sigaev.ru
WWW: http://www.sigaev.ru/
