[analog-help] OS unknown

[gsheu at tunl.duke.edu]

Our group have been using Analog since Apr. 2002 to see how often people 
access our website. In our reports, the average monthly #reqs under "OS unknown" 
in "Operating System Report" is as following:

     Year       #reqs
------------------------
     2002        1600
     2003        2400
     2004        4500
     2005        8300
     2006       19000

You can see that the number is increasing each year. It seems not 
reasonable to count those #reqs as people "actually" using our 
websites. How can I determine if these OS unknown includes robots 
or search engines? How can I decrease the OS unknown numbers?

Thanks for your halp.

Grace