7.4 Counting Unique Titles
Two COUNTER Metric_Types count the number of unique titles that had a certain activity: Unique_Title_Requests and Unique_Title_Investigations. These metrics apply only to books, including Data_Types Book and Reference_Work.
For the purpose of COUNTER metrics, a title represents the parent work (book) that a specific content item is part of. The title MUST be identified using a unique identifier (e.g. an ISBN for a book) regardless of format (e.g. PDF, HTML or EPUB).
While the method for counting book usage in R5.1 at the item level is different than it was in R5, the method for counting title-level usage is unchanged. That means Unique_Title_Requests and Unique_Title_Investigations are comparable across report providers and across releases.
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: 2024-06-15 13:35
IP address: 18.104.22.168
User agent: Mozilla/5.0
Generated session ID: 22.214.171.124|Mozilla/5.0|2024-06-15|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.