Combining Information from Multiple Internet Sources

3. Algorithms
This part of the thesis provides the detailed description of the three information combination
approaches. This chapter also describes any helper routines that are used by those approaches. Each
of the main algorithms for obtaining the final answer has its pseudo code included as well as the
activity diagrams.
3.1 Game theory method
This sub-chapter presents the Game theory method. This algorithm was used before in the
NeurAge system [9] and had to be adapted to suit the purpose of combination of the data retrieved
from the Internet. In its original form agents were supposed to vote for certain classes of data; here,
they are voting for certain URLs. The confidence values from the original algorithm have been
replaced by the URL ranks according to the algorithm described in section 3.4.1. Also, in its
original form agents were yielding one class as the final answer. In the adapted form agents are
returning 10 URLs in sequence, where any next iteration starts the whole process from the
beginning, however without processing the URL which was already selected. This does not violate
the main assumptions of the algorithm and this was stated by Edyta Szymańska of Emory
University, Atlanta by means of personal communication.
In general, a game is defined as follows: it consists of set of players, set of moves
(strategies) and specifications of payoffs for each combination of moves. In case of algorithm which
will be presented in further section game is a normal form game that is defined as follows:
There is a finite set P of players, which we label { ,2,..., m}
1 .
Each player k has finite number of pure strategies (moves)
S k
= { 1, 2, ..., n k
}.
A pure strategy profile is an association of strategies to players,
that is m-tuple
r
σ = ( σ , 1
σ
2
,...,
σ m
)
such that
σ
1
∈ S1, σ
2
∈ S
2
,...,
σ
m
∈ S m
Let strategy profiles be denoted by Σ
A payoff function is a function
F : Σ → R
whose intended representation is the award given to a single player at the outcome of the
game. Accordingly to specify a game the payoff function has to be specified for each player in
P = 1,2,...,
m .
the player set { }
Definition. A game in normal form is a structure
( P , S,
F )
Where P = { 1,2,...,
m}
is a set of players, S ( S , 1
S
2
,...,
S m
)
sets, one for each player and F ( F F ,...,
)
= is a m-tuple of pure strategy
= , 1 2
F m is a m-tuple of payoff functions.
Listing 3.1.1 Definition of the normal form game
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