ABSTRACT Relational fuzzy clustering (RFC) algorithms prove very useful in Web user session clustering
because Web user sessions may contain fuzzy, conflicting and imprecise information. Though RFC algorithms
are very sensitive to cluster initialization and works only if the numbers of clusters are specified
in advance. However, at all times, the prior initialization of a number of clusters is not feasible due
to the dynamically evolving nature of user sessions. Therefore, estimating the number of clusters and
initializing suitable cluster prototype are a significant performance bottleneck in this method. In this paper,
the discounted fuzzy relational clustering (DFRC) algorithm is proposed to address the major constraint
of RFC. The DFRC algorithm identifies Web user session clusters from Web server access logs, without
initializing the number of clusters and prototypes of initial clusters. The DFRC algorithm works in two
stages. In the first stage, DFRC automatically identifies the number of potential clusters based on the
successively discounted potential density function value of each relational data and their respective centres.
In the second stage, DFRC assigns fuzzy membership values to each data point and forms fuzzy clusters from
the relational matrix. The DFRC algorithm is applied on an augmented session dissimilarity matrix obtained
from a publicly accessed NASA Web server log data. The experimental results are evaluated using different
fuzzy validity measures. The extensive experiments are performed to test the effect of various parameters,
including accept/reject ratio and neighbourhood radius on the performance of DFRC algorithm. The results
were also compared with fuzzy relational clustering algorithm using cluster quality measures. It is observed
that the quality of generated clusters using DFRC is superior as compared with that of RFC.