39. The device of claim 36 wherein the preprocessor includes a filter for filtering data based on the identification of the times.
36. In a system including a server for servicing requests for resources, a device for generating a resource transition probability model based on resources referenced, the device including: a) a usage log generation unit for generating usage logs including information regarding (i) an identification of clients which requested the resources referenced, (ii) an identification of the resources referenced, and (iii) an identification of times when the resources were referenced; b) a preprocessor for defining sessions based on the information regarding the identification of clients and the identification of the times; and c) a resource transition probabilities determining unit for generating resource transition probabilities based on the identification of clients, the identification of resources retrieved, and the defined sessions.