Authors:
            
                    Madhuka Udantha
                    
                        
                    
                    ; 
                
                    Surangika Ranathunga
                    
                        
                    
                     and
                
                    Gihan Dias
                    
                        
                    
                    
                
        
        
            Affiliation:
            
                    
                        
                    
                    University of Moratuwa, Sri Lanka
                
        
        
        
        
        
             Keyword(s):
            Web Usage Mining, Pattern Mining, Regular Expressions, Anomaly Detection.
        
        
            
                Related
                    Ontology
                    Subjects/Areas/Topics:
                
                        Classification
                    ; 
                        Clustering
                    ; 
                        Combinatorial Optimization
                    ; 
                        Feature Selection and Extraction
                    ; 
                        Pattern Recognition
                    ; 
                        Similarity and Distance Learning
                    ; 
                        Theory and Methods
                    
            
        
        
            
                Abstract: 
                Mining web access log data is a popular technique to identify frequent access patterns of website users. There are many mining techniques such as clustering, sequential pattern mining and association rule mining to identify these frequent access patterns. Each can find interesting access patterns and group the users, but they cannot identify the slight differences between accesses patterns included in individual clusters. But in reality these could refer to important information about attacks. This paper introduces a methodology to identify these access patterns at a much lower level than what is provided by traditional clustering techniques, such as nearest neighbour based techniques and classification techniques. This technique makes use of the concept of episodes to represent web sessions. These episodes are expressed in the form of regular expressions. To the best of our knowledge, this is the first time to apply the concept of regular expressions to identify user access patterns
                 in web server log data. In addition to identifying frequent patterns, we demonstrate that this technique is able to identify access patterns that occur rarely, which would have been simply treated as noise in traditional clustering mechanisms.
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