How Sawmill calculates Durations

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How Sawmill calculates "Durations"

User 'A' visits a current affairs/news web site and spends one minute browsing and then settles on a news item, spending seven minutes reading it then browsing for another two minutes and reading the next news item for a further eight minutes, then exiting by closing the browser. Here is the time line:

  • 11/04/2005 16:12 - arrive at homepage and navigate to a news item
  • 11/04/2005 16:13 - read news item 1
  • 11/04/2005 16:20 - navigate to next news item
  • 11/04/2005 16:22 - read news item 2
  • 11/04/2005 16:30 - exit (close down browser - no further activity for 30 mins)

With the session timeout interval of 30 minutes (this can be changed by the Sawmill administrator), Sawmill will count 1 session with a 10 minute duration, with the 2 news item pages having durations of 7 & 8 minutes respectively.

This calculation shows the problem of duration counting in all log analysis software. Since there is no reporting of the exact time the user left the site (there is no log entry for the 16.30 'exit' as closing the browser does not leave any record in the server logs), we have no way of knowing when the user exited, so we count from the last known time which in this case is the start of reading the second news item, 16:22.

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