7.4 Counting Unique Titles
Some COUNTER Metric_Types count the number of unique titles that had a certain activity, such as a Unique_Title_Requests or Unique_Title_Investigations.
For the purpose of COUNTER metrics, a title represents the parent work that the item is part of. When the item is a chapter or section, the title is the book. The title MUST be identified using a unique identifier (e.g. an ISBN for a book) regardless of format (e.g. PDF or HTML).
The rules for calculating the unique title counts are as follows:
If multiple transactions qualifying for the Metric_Type in question represent the same title and occur in the same user-session only one unique activity MUST be counted for that title.
A user session is defined any of the following ways: by a logged session ID + transaction date, by a logged user ID (if users log in with personal accounts) + transaction date + hour of day (day is divided into 24 one-hour slices), by a logged user cookie + transaction date + hour of day, or by a combination of IP address + user agent + transaction date + hour of day.
To allow for simplicity in calculating session IDs, when a session ID is not explicitly tracked, the day will be divided into 24 one-hour slices and a surrogate session ID will be generated by combining the transaction date + hour time slice + one of the following: user ID, cookie ID, or IP address + user agent. For example, consider the following transaction:
Transaction date/time: 2017-06-15 13:35
IP address: 184.108.40.206
User agent: Mozilla/5.0
Generated session ID: 220.127.116.11|Mozilla/5.0|2017-06-15|13
The above replacement for a session ID does not provide an exact analogy to a session. However, statistical studies show that the result of using such a surrogate for a session ID results in unique counts are within 1-2 % of unique counts generated with actual sessions.