Input: the time interval threshold , distance threshold , atypical
       dataset R
  Output: The basic atypical cluster set basic_set
1    repeat
2   randomly select a seed record r from R;
3   retrieve all the atypical connected records from r w.r.t. and ;
4   group those records to form an atypical event E(S; T); 
5   initialize basic cluster ;
6   foreach sensor do
7    compute the sensor severity ;
8     add to ;
9      end
10        foreach time window do
11      compute the time window severity ;
12      add to ;
13   end
14   add to basic_set;
15   
16  until ;
17  return basic_set;
Algorithm 1: Basic cluster generation.