Combining Information from Multiple Internet Sources

is multiplied by 0.01. 3
If the algorithms could not be started; the application creates a combined result set from all
result sets without URL repetitions and such large set is displayed with a possibility to provide
feedback. The URL which is considered to be the best can be marked as feedback and it is sent to
the application, which uses it as an anchor to start weights calculation process.
Input: Result from feedback; initial result sets
Output: Map of weights with corresponding agents
BEGIN
1. find the agent whose result set contains the result from feedback,
set his weight to 1
2. for all other agents:
( i ) w
find d( r , r )
W[
i]
=
where
r
( i) ( i )
− d
r
w
( r , r )
( i)
( i)
w
( r r )
d , is the number of different URLs between the result
set of agent i and the “winner ” agent (note that those in case of
ad joint result sets will be equal to zero)
3. return weights
END
Listing 3.4.2 Weights calculation for Game theory and Auction methods
3.4.3 Adapted Levenshtein distance
Next listing presents the adapted algorithm for finding Levenshtein distance. An adaptation
of this algorithm was used in the application for calculating distances between result sets. The
algorithm is simple but at the same moment it is very fast and provides well and easily interpretable
results.
In its original version it is an edit distance – measure of distance between strings. It finds
how many basic operations are needed to transform one string into another. “Basic operations”
mean the following:
• deletion of a character from the string
• insertion of a character to a string
• substitution of a character with another character
This distance was applied to measure the distance between result sets. Adaptation of this distance
was as following: strings became result sets; characters became URLs. Having this translation, one
3 As for the previous case – this functionality was disabled for the tests presented in chapter 4. Weight of every search
engine was equal to 1 – URL ranks were not altered.
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